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- เผยแพร่เมื่อ 30 ก.ย. 2024
- More than you ever wanted to know about 64mm vs 69mm valves in 139QMB / 1P39QMB / GY6 50 scooter engines. What does it mean? How can you tell which you have? Why does it matter? All answered in detail.
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##ScooterDIY #139QMB #GY650
Really super well explained with absolutely nothing forgotten in the difference between the two cylinder heads and their rocker arms. Nothing extra can be added to this extensive tutorial. I have both lying and everything is correct to the last detail.
thanks for the awesome video man! you are essential to many people learning
Very good and precise info and a pleasure to watch. Very easy to understand
I have a 49cc Linhai Joc I upgraded the engine with a 50mm bbk, and after about a 100 miles my intake inner springs broke,have new ones ordered and now I found this video telling me that both heads use the same spring sets..lol..looks like I got some extra spring in case it happens again..thanks for the info...
Bought a full 90cc big bore kit that came with a new head and 69mm valves. It came with replacement rockers (different ratio) to use on the cam from the old 64mm head. Thanks for the channel. I buy abandon/weathered GY6 scooters and rebuild them.
be careful with 90cc and above because they can overheat
Its not a 90cc the highest a gy6 can go bore wise is 52mm 88cc and anything bigger than 72cc will not only overheat but overstress the cranknand bearings tonthe point that the kit wont last any longer than 3000 moles or so
I have a scooter and when I hit full throttle on the stock engine the handle bars feel like they are slanted
Great video as I was wondering the same thing. Basically there is no performance gain, but the 69mm head allows more room for porting.
There is always more room for porting when you're 69ing 🫢🤭🫠🤣
Now that's an eye opener! Great job.
DUDE!! You are amazing! You did the most sensational job of explaining this subject. The fact that you cut and painted the heads alone is almost unbelievable. Now I know to look for ported heads for better performance. There isn't anybody that could do a better job than what you did here. Thanks again!
Awesome video mate! I was impressed by your investigative motivation, dissecting cylinder heads is going above and beyond. :D Really enjoy your videos man, looking forward to the next one.
Thank you!
iv had a scooter for 4 years and built my 80 cc motor and thought i knew everything, gy6 info never ever ever stops
Great video! I bought a Viarelli matador and hade to buy a new cylinder head. I incorrectly bought a head with 64 mm valves and original rocker is for 69 mm. When I contacted racing planet they said that I could put the nut for the adjustment screw under the arm instead. Could that work. Any one tried this? Thanks.
Excellent video 👏. Solved my problem. Bought a non-runner with no compression. Previous owner installed a BBK and it wouldn't start. 64mm rockers on 69mm valves. Valves would not close even with tappets removed. Thanks 🔧👍
wait a minute..... did you say the 64mm valve is shorter than the 69mm valve... ARE YOU FUCKING KIDDING ME
This video really helped me out my cylinder head on my moped is bad I had to replace it.I didn't know what size my old one was so I got a 64 mm now I know my old one is is 69 mm so now I have to order 64 mm rocker arms.
BRO KEEP TEACHING USSS YOU ARE THE BEST MUCH LOVE FROM ALBANIA 🇦🇱🇦🇱
I had 69. It's easier to lash on maddog. For sure. I got a bbk that's 64
What head would be best with an 80cc kit?
Whatever matches what you have is the easiest. Then you don't have to worry about mismatching valve lengths.
Nice video. Thank You :)
When upgrading a 50cc with a big bore kit, does it matter if one gets the 64mm kit or the 69mm kit?
Other than porting, is there an advantage/disadvantage to either such as more/less power, speed, acceleration, fuel use, wear, noise, vibration, etc?
What's the purpose of having both on the market?
Or is it just basically a longer/shorter version for no reason.
+Siber Industries The only reason it matters when you get a BBK is if you'll need different rocker arms. As long as you have the right rocker arms for the head that you choose with the BBK, you'll be fine. I don't really know how the aftermarket heads are setup. Unless you are willing to get into a lot of port work, you probably wouldn't notice much difference from 64mm to 69mm.
I'm not really sure why there are 2 versions. It could be that 69mm is intended to be an improved head or for all I know it could be that they have 69mm long valves around from some other application and decided to use them. Sorry, but I just don't know.
It only matters because that's the size that matches the top half of the engine block.
Really , if your engine is new when you do the bbk,
You can usually save money and just reinstall
your original top half of the engine assembly onto the engine.
Just be careful , if also
replacing cam , that might
need new custom top half
of engine.
Valve heads just got easier lol great video
Thanks!
Which one makes more compression? I am looking to get the 52.4mm BBK but don’t know what head to use for more compression the 64mm or the 69mm
Shouldn't matter. That's about combustion chamber size, deck height, piston design...
Hi i watched the video twice, and must have missed the part i was looking for. I am looking to buy a bike with a 139QMB engine, and I am planning to get a 80cc big bore kit for it. Is that engine 64mm or 69mm. i know u mentioned that sometimes the P in the engine name means 69mm but then you said not always. Please help, thanks.
It could be either one. Definitely all P engines aren't a certain valve length, and all non-P engines aren't either. That would make it too easy on us I guess.
You'd have to disassemble to be absolutely sure. I have a BN139QMB motor with 69mm valves
Will it cause problems if I use 50mm cylinder and 52mm cylinder head? To reduce the compression ratio
You'd be better off with a matching bore diameter or smaller bore diameter and proper combustion chamber size. The sort of mushroom shape up there won't be good for performance and could encourage detonation.
Ok
So basically porting is needed which is why there's a 69mm valve
I don't know the actual reason for the differences. It works out well if you want to port though.
nice job man!! very in depth. thank you.
Why is there a 64mm head and 69mm head? Couldnt they have left it with one head instead.? 64MM is old type? 69mm new type?
I don't know why. Could be any number of reasons and I'd just be guessing.
You do a Great job explaining the work ! Thank you ! You've been a GREAT Help to me 👍
Thanks. Glad the vids are of use.
Excellent Video man! Absolutely Excellent! 👍👍
Awesome Job its just what I wanted to know thanks, just wondering could you tell if it looked like one head would Flow better then the other ?
Daniel Lee I'd guess they'd be similar, though it appears there's more potential with the 69mm valved head.
And hey bro I keep getting the wrong rocker arms what miligrams do I need for a GY6 90cc Big Bore Kit from Taiwan? You're always there for us man I'm going to need you again bro sorry. I keep getting the wrong rocker arms now I know you know which one I need if you can send me the link as well I appreciate it bro.
It depends on your engine. There should only be 2 types. 64 and 69. Order whichever you don't have now if it's wrong.
@@49ccscoot well I have a 93 CC and it's a 139 GY6 of course and it's a 4-stroke
@@49ccscoot and like I said before I have a Taiwanese 93 Big Bore Kit from Rolling Ridge bro
@@marineboy4181 Right. Did you watch this video though? The 139QMB can have either valve size, so you need to check as shown.
@@49ccscoot and sorry bro yes I watch the video sorry for the late reply I had to get up to go to work. I talk to the person that I ordered the 90cc Big Bore Kit from and he said that I needed a 64 so I ordered it 64 mm not 69
intake: how many mm is the valve pitch?
Exhaust: how many mm is the valve spacing?
for best performance?
My buddies Q6 icebear trike we did a 50mm bbk bolt on build.. And when i was called in to do timing and 69mm head i could not change out rocker arms the pins would NOT come out (only 40miles on bike) and 1 of the arms (i think intake) was very tight and did not move as freely as I believe it should up and down.. I told him he wanted it on so we sent it.. Now it seems like its over reviving hitting way high RPMs before getting to speed. Could that rocker arm be the reason?
If not what issues could pop up due to thight arm thight pins?
hello brother, I know this might be little ot question but: I have kymco super8 4t 50cc scooter which is in stock(only cdi unrestricted). What would happen if I installed a9 camshaft to the stock scooter? would it improve performance or just be waste of money and time? thanks.
What valves should I habe on a 2017 gy6 qmb139 factory tokens they come with 64s just wanna make sure tho
So I got the 52.44mm big bore kit from Naraku the valve springs are seated in a galley so that head will use 64 mm rocker arms right
What if I was to put a 64mm valve on a 69mm head? Would it run the same?
I'm not sure if they are interchangeable because of the way the head is cast/machined to accept the different valve lengths. It would probably throw off the specs like seat pressure and may even lead to coil bind. Never tried it.
I need your help badly....i just need to know what type/ size/ matching parts to buy!!?? Valve-intake-oversize carb-air filter-etc
What about bn139qmb motor. Are those motors any good?
Same thing AFAIK. Some manufacturers use a little different lettering. BN is made by Znen.
Don't do a 80 bore kit without doing a matching 80 head. Or you'll have not much improvement
Super interesting. I did always assume it was the valve size, but ofcourse that's way too big. Lol. Just never really looked at it. But, I'm so glad you showed the cutaway because I have both, and want to port a head for a performance build.
What happends if the valves are not 100% alligned with the rockers? Will it still work but do you loose performance?
The 69 looks like a much better head over all. That extra meat in the head will reduce valve deflection and seat distortion at high RPM?temp. It should also make the cam slightly more stable
Good points. Thanks for the input.
***** Thank you for cutting heads in half.
Thank you for that been trying to work out which one I had as one bbk states only for 64mm head. Milly
So you can port the 69 mm heads a bit more, without running into the spring pocket! I had a tiny issue with this, I'm looking into larger valves!
Big Thanks to You! Very easy to understand. Hello from rus)
A bit of epoxy. Will fix the intake if you only have a tiny hole like I got into, but the exhaust you either weld it or scrap it!
I am so thankful for this video!!! Great job so informative!!!!
New video NICE:D:D :) thumbs up
Thanks!
Can we add watercooling to the 4t engine
There's no reason that it couldn't be done, but I don't know if there are parts for the 139QMB. There is definitely stuff to make liquid cooled GY6 150cc+. Maybe some research into other stock liquid cooled 49cc would allow you to find parts to be adapted.
very good contribution thank you it would be very good that you translate them in Spanish so that Latinos understand more thanks
I have a hose coming off the front of my engine?... It's in front of my carburetor if I open the little panel in front of my seat. It is not connected to anything and I can tell it used to be clamped on something as the hose end is widened and I see indents where the clamp was, what is that supposed to be connected to?
Is it an air filter/leading to an airbox? If so, the carb would be open (no filtration) till you get it hooked back up.
@@49ccscoot it was leading to the air box...I put a uni air filter, did an emission delete and put a little mini air filter on the end of that hose. Hope it works and it seems fine
Does anyone know if we can install two intake valves instead of a smaller exhaust valve?
Thanks a lot bro you are a good dude for sharing your knowledge with us.. Saved me a lot of $$
Does a 69mm valve head give you any performance increase? or what would be the point of going from a 64mm to 69mm setup?
Ignore this post, I'm on some forum right now reading your post responding to a similar question lol
Hello how much does it take to set the valve game?
What size of jet should you install in the carburetor?
What weight of rollers do you recommend for the drive?
For the clutch that advise me?
Thank you for your advice
Valve adjustment :
th-cam.com/video/s0K-ytyjOFg/w-d-xo.html
The carburetor should be tuned. 1 jet size doesn't fit all :
th-cam.com/video/K5j8gHg5kMc/w-d-xo.html
www.49ccscoot.com/faq/carbtune.html
Again with the rollers, I recommend tuning. 5g sliders are pretty common for a stock 139QMB upgrade though. I prefer sliders over rollers. :
th-cam.com/video/K5j8gHg5kMc/w-d-xo.html
Get a few sets of springs for the clutch and see which work best. I know these aren't the answers most want, but IMO anyone that says X jet, X rollers, or X springs are the best for all haven't done enough tuning. Many will be happy with generalized guesses, but also many will find lackluster performance.
Thank you very much for your reply and advise fast.
You're welcome. Good luck with your project.
I recently ported the piss out of a 64mm head. Did not go thru.
Could be that they're making heads different. I'm sure there are quite a few variables between Chinese factories putting these out. Could be that you didn't get into the thinnest areas much. Could be that you have a paper thin wall somewhere unbeknownst.
@@49ccscoot I didn't take much material out of the area where it's thinnest, mostly bowl work, but my head is from a 2005 SunL.
Not really sure when they started making these 139QB engines, but it's quite old.
ty
You can change them, from long to short.
So you can change your valves from 64v to 69v in the cylinder head without buying a whole new cylinder, head????
Que buena informacion! Muchas gracias! 😃👍🇦🇷
Please write down what you speak, and we will translate it into our language. Okay
TH-cam should do this for you. I can see subtitles auto-translated in many languages. I go to the settings (gear) icon. I turn subtitles on, and for me it will only say "English (auto-generated)". I choose that. Once I have done that, I can go back to subtitles and auto translate appears. Then I can choose from lots of languages.
@@49ccscoot TURKISH Language. ok. thanks
Very interesting. Every day learning something new.
AMAZING VIDEOS....THANKS
So i have a quick question im gonna buy a BBK FOR MY YN50QT-8
(gy6 50cc) scooter today i wanna get the whole package:also including a oversized race carb w/ butterfly choke & air filter, valve head, cam shaft, piston, rocker arms, assembly,coil, cdi, variator, belt,clutch & buy a jetting kit too..etc CAN U PLEASE TELL ME EXACTLY WHAT TO ORDER & WHERE TO ORDER ALL THAT I NEED...??? PLEASE🙏 I CAN PAYPAL YOU 20$ IF U CAN MAKE A PARTS LIST OR TELL ME WHAT TO ORDER SO EVERYTHING FITS/ MATCHES & MOST POWER/ TORQUE!??? OH and i want it to get up and go GOOOOO off the line....accelerate super fast & TOP END!!🙏🙏🙏 THANK YOU SO MUCH FOR YOUR HELP I KNOW NOTHING ABOUT PARTS & ENGINES IM LOST....LOLOL
The bigger and more powerful you make it, the more likely it is to fail prematurely. The 50mm and larger bores do well for power, but are known to ruin crank bearings in short order; especially when revved out to make max power. 47mm (72cc) big bore kits are the best for most riders IMO, because engine life doesn't usually suffer in the same way. 47mm BBK, A9 cam, stock carb/intake with tuning, and CVT tuning will make a decent setup for most. Add a performance variator for even better results. Some 47mm kits may require a head with a larger bore or some spacing (usually extra gaskets) to keep compression in check. They vary. I would suggest contacting a company like PartsForScooters or ScooterTuning and telling them what you want. They have been trustworthy places for me and stand behind products. They should be able to get you going with a setup that will make you happy. I just haven't messed with enough kits recently to tell you for sure an exact setup first try.
So say I put a 100cc kit in and they send me a head with 69 valves and I have 64mm valves will the 64mm head work ok on a 100cc cyinder
As long as you match up the 64mm head and rocker assembly, or the 69mm head and rocker assembly, it should work.
Ok so the 100cc kit showed up with a 64mm valves this bike has 69 so I had a brand new 69mm head laying around so I put that on and everything lined up ok just hate that I couldn't use the head that come with the big bore kit look like the valves where a tad bit bigger on it I'm doing this kit for a customer at my repair shop he didn't leave me enough in the budget for new rockers so the 50cc 69mm head is going to have to work
@@christopherdarrough2667 Just FYI, a local shop used to do "100cc" kits (50mm bore) and use stock heads. They stopped doing that after a bunch of customers had engine failures, and after that larger heads were mandatory to keep compression in check. At least do yourself a favor and do a cranking compression test and if it looks really high, see if a thicker gasket or additional base gaskets may be an option. Doesn't look good on you when there's a meltdown right after you build the engine for them.
Thanks for your informative video. I recently upgraded my gy6 scooter from 80cc to 100 cc cylinder. The mechanic that worked on it kept the 64mm cylinder head. He handed me two 64 mm valves with ol seals told me he replaced them. However I couldn’t notice any change even lost power at accelerations. I began watching videos when I stumbled upon yours. I suspected there is an issue with valve clearance. I checked myself the intake was no lash at all. I fixed it to 0.08 mm whereas the exhaust was too loose 0.15 mm. I fixed it to 0.10 mm. The issue is I don't know whether I have 69mm valves on this 64 mm cylinder head. The tappet nut in the exhaust screws just fine whereas in the exhaust the nut screws out as in your video. I guess there is a problem with tha angle. Even though the scooter runs great except for some loss of power from now and then and some spluttering from the exhaust. What would you recommed? Thanks again for your great tutorials.
Number one would be find a new mechanic. I'd try to take a close look at how the valves interact with the rockers. They should meet up flat against each other. If they don't you may have a mismatch or other problem.
With a long valve there is less valve guide in the port blocking flow, and the port can be raised when porting, to gain performance, you can gain some performance on either, by adding an additional shim under the springs, only one extra. So 2shims, you can go with 3shims, but you must check clearance, the springs can bind, but only if there is signs of valve float. More pressure only eats power! You just need enough pressure to control the valves, if it was me, I'd make the valves even longer, 74mm, and make the ports even higher in the head, nearly 15mm on the inside, to get a better shot at the valve, and spread the valves out from each other. But they would not work with a stock bore, 47mm and up, maybe go 4x -18-19-20mm exhaust valves, and 22-23mm intake, valves, with dual cams, with rocker followers, the intake side cam working the exhaust, and vice versa! Making it easy to put the sparkplug in the center, allowing two cylinder engines to be built, or more! A gy6-85 4cylinder haha!! 81-83cc x4
If I had a mill and lathe I'd build a 2cylinder with 52.4 bores, and big valve heads, with a8-a9 cams, and single 30mm carb if I even had a good drill press, and a welder I could weld aluminum with, .maybe even build a stroker crank! Get about 100cc per cyl from it, I think it would perform better than a gy6 150 big bore, nearly 200 cc, being it fires two cylinders,
If you could just take 1 cylinder off of a sportbike and graft that to the CVT...
thanks
how do i know if rocker arms is correct for 64mm or 69mm? I threw away my original cylinder head (kymco agility 50 4t R12 2007) now I have a malossi 52mm cylinder and 52.4mm naraku v2 head with 64mm valve.
You should be able to look them over when installed and see if there are alignment issues. Someone can probably tell you what Kymco had stock, but I'm not sure.
I want to buy thee best/ most power bbk on the market
I have a scooter taotao zummer 1p39qmb which valve application uses 64/69 sorry I do not know English I do not understand the video well
Most likely 69mm.
Can you please tell me if I put a 47mm bbk on my gy6 139qmb 50cc bike do I need a oil decompression kit ? And thanks much. Sir
No, you don't need that.
my have 80 mm valves but its a buggy with differential 157qmbj code engine, sucks for finding parts
I don't know about that exact code. It's close to the GY6 150. If you haven't already, make sure it's not just a GY6 150, because those have an abundance of parts out there. There are variants of the 150 that I think have 80mm valves, like maybe the GY6 B. Worth doing some searches if you haven't tried that already.
Hi I opened my valve cover to check on my valves and I noticed my head nuts were loose so I tightened them but a little too much and one of them put a crack on my assembly so I ordered a new one a 64mm even tho I have a 69mm I did not know until this video. But when I was installing it the cam shaft would not go in place every time I pushed the assembly down the cam would not go in place and tilt up and when I tightened it the engine did not spin is this because it’s a 64mm assembly in a 69 or did I do something wrong because I tried to push the cam back and forth and nothing worked out
You need the proper assembly to match what you had. Also, make this a learning experience and torque to spec when dealing with engine fasteners whenever possible. Stuff happens even then, but much less.
@@49ccscoot so basically I should get the 69mm sense my engine is 69mm right I just want to make it clear before I buy and thank you so much for your reply I will definitely tourque it to spec thank you agian
@@sahelgmaing601 Correct.
@@49ccscoot thank you so much you have helped me a lot have a wonderful night
Thanks for this video! very helpful
Thanks for posting this video. It was very informative and very helpful.
this is a great video and thank you for posting it. my question is what is the advantage of one over the other. if they are the same diameter but different length is there a difference in the way the motor runs. more air flow with the 69mm valves? I'm not doing any porting but I already have the 64mm valve head and 100cc bbk. thanks again.
I would suspect that real world difference would be very minimal. Either one could have advantages and disadvantages. For most of us that don't need to be incredibly competitive, either one should be fine.
What's the point if it doesn't have a performance difference??
TBH I don't know why there are two versions. Maybe someone decided that the head needed more material below the valve spring seats?
I know this is a random question but what do you set your valve cap on a 100cc bar kit for 50cc engine
Most of the time I do 0.002"in/0.003"ex. They don't need more clearance just because the bore is bigger.
I bought an 69mm valve head from amazing installed it onto the gy6 50 Cc and it sounds like it has no compression what so ever I also bought another one from a different website and it did the same thing what do I do
Nevermind I kept watching longer into the video and u explained the rocker arm situation
GREAT VIDEO. I only have one question. Will the valve cover for a 64mm valves fit a 69mm setup?
It should.
Im curious, from what I am seeing there are two different heads for the same engine. What is making the difference? I have a 2014 atm50-a1. Thanks
+Ryan Szumiesz The difference is explained in the video. If you mean why are they making them different, I'm not sure. Your TaoTao should have the 69mm valves. Mine does and anyone I recall posting about it says they have 69mm valves so I believe that to be the standard for TaoTao.
If i put a 100cc bore kit how come some come just the cylinder andnpiston and some come with head wich should i use
They can fulfill different needs/wants for engine building. Not a good idea to use a "100cc" kit with a stock head, so if you don't have a suitable head then you should get a kit that includes everything.
I have already put a big bore kit on my gy6 from 49cc to 100cc how big can I go.
100cc is already bigger than you can get, so that's pretty good. The last time I checked, the largest setup was about 95cc with a 44mm stroker crank and 52.4mm bore. Unfortunately a lot of sellers call their big bore kits 80 and 100cc even though they are not.
49ccscoot.proboards.com/thread/2953/displacement-torque-tables-gy6-139qmb
Some people confuse valve height with valve size when refferring to a "big valve head" i wanna know about the big valve head, are these better? Does the larger valve diameter make a difference?
It can help, but the worst part is that sometimes they make the combustion chamber so big with big valve heads (also generally intended for big bores) that the compression change seems to kind of make it even out. This is what people on my forum are reporting.
Hi! I wanted to ask if you know how to straighten bent wheel disks not the rim but when theyre bent in the center it's not much but still annoying and feels like my scooter is losing power because of that. Do you have any solutions for that ?
Sorry, but my best advice would be to replace them. Usually can find them fairly cheap for common scoots on eBay or you can try the classifieds section on the forum at 49ccscoot.proboards.com
Is there a way to tell what valve size with out disassemble the motor ? Like by the vin number or something ?
If you would've watched the video, you'd know.
Thaks, that's important...
Спасибо! А как распознать на вид сами коромысла ?
How tricky with all just the different lengths.. ugh!
Also i wounder, if i change to 69/64 will i have to change the timing chain? alongst with talking about timing chains.. apperantly to my service schedule on my scooters manual, i shall replace the timing chain at 4000km (about 2500miles) and the bike got about 1900miles on it.. do i really have to replace the timing belt that early? concidering its normally an item in cars/motorcycles that never need to be replaced more or less.. and doing so, is it hard, like does one have to split the engine or something similar?
The timing chain should be the same because you aren't changing the distance from the cam to crank or the size of the cam gear. Basically your valves are just raised 5mm. The head, guides, valves, and rockers are all specific to each style (64or69mm). Otherwise swaps shouldn't be an issue. The timing chain should be alright at 2500 miles. If you don't see an issue with it, like it's really loose, you should be fine. Even if it's loose, first I'd check the tensioner.
***** Alright, thanks man! :)
I have a BN139QMB engine with 69mm valves.
Adly/Bintelli?
Really big question I need help with. I have a 69mm and a 64mm head, I was running the 69mm head but it was for a smaller piston size and I wasn't the one that changed it out. I didn't run it long and noticed the tick from it and it left the imprint from piston in the head. I got a used replacement from my buddy that's for the 100cc which is what I needed (49cc with the 100cc big bore kit) I got it and it's got 64mm heads. Can I put the 69mm valves and spring on the 64mm valves. I got both sizes of valves and rocker arms. I just have to change the cylinder head but one and to keep the 69mm valves as I've been told and read they run better with the big bore kits. Only thing is in the video you pointed out the raised aluminum platform on the 69mm heads. Will that make a huge difference or will I just be putting 69mm valves on a 64mm head case leaving me a gap on my valves?
Replace the rocker arms or rocker assy and the 64mm head should be fine.
90GTVert awesome thanks wasn't sure if it would effect performance
What would be the valve clearance for a big bore from a 49cc? I acquired a scooter and the seller said it has a big bore kit, I did get the spare cylinder, rocket, head. I assume it was done right.
I set most to 0.002-0.003". 0.005" would be about the max.
Exhaust and intake ? Btdc ? Or tdc
Okay, so lets so I buy a big bore kit that is a 64mm kit and my scoot has 69mm heads installed. What are my options? Can you just buy some 64mm rocker arms and swap them out? I'm not exactly clear on that. I know nothing about engines, I have a small scooter project just to try and learn about mechanics myself.
You can get the different rocker arms and swap them, or a whole rocker assembly.
You can use you whole 69mm head, rocker assembly included and just purchase the 80cc or 100cc piston and piston body.
can i use my stock head 64mm on my 50mm big bore kit or dose it have to be a 69mm head
Stock head would be OK aside from the small combustion chamber. Could create too high compression and lots of heat and/or detonation.
For 64mm valves. What adjustments do I need to tune to. I cant fine any right answer to adjust it To.
I use 0.002" intake and 0.003" exhaust on 64 or 69mm valved 139QMBs in most cases.
@@49ccscoot hot or cold?
@@rallyscoot Cold.
I need your help please . I have a Icebear scooter . So far I have a 80cc goofit performance 47mm bbk and head 64mm . A 18mm carb. With a 33mm idle jet a pod air filter 1500 clutch spring 6.5g sliders and a new cvt belt . And a over sized pipe and as free flow muffler And I am at 2000 feet above sea level . I only ask how big of a main jet to start out with . So as not to run my bike to lean . And I will tune it from there . And thanks . By the way I did check the compressor cold with the starter and it is 150. Thanks
I usually start big. If it's way too big, it will be obvious with sputtering and running issues. Work down from there in small steps are record results till you see a trend in results that shows you what is working. Could be too much, but I'd prob start at ~100 main jet. As long as that didn't act lean, go for 95, 90, etc... Once you figure out which 1-2 jets are working best that way, then you can try to fine tune if you'd like, with jets like 92.5 and 97.5 or if you're really motivated you can make 1 number changes. Extreme fine tuning is not that useful in many cases, because weather varies so much that it's going to be off day to day to some degree anyway and even more as seasons or elevation change.
Nice video! So i can mont. any 100cc big Bore made for the gy6 engine. Even If you have the 64 or the 69? Its just the head thats the diffrent? Its that right?
The cylinder and piston kit should not be different.
Thanks! :)
I have noticed that the 69mm valve heads have the port for the EGR drilled and the 64mm heads don't. I don't know if that is true of all 69mm & 64mm heads. Also it would appear on the 64mm, the head intake & exhasut ports are already opened up a little more than on the 69mm heads. It makes you think the 64mm heads would flow better. Fantastic video!
There are 64mm and 69mm emissions and non-emissions heads available.
Thanks.
Excellent, extremely informative.
Such a good channel...top quality material 🖒🖒🖒
Thanks!
Is there a 4 valve head for the 49cc or is it possible?
If you google "4 valve 139QMB" you should see a 4V head. They're out there, but I don't know anything about them.
So if I grab a basic 72cc BBk with 69mm head set. It should work fine on my stock setup either way correct? I plan on using my factory head as I was informed it should be fine if I keep the BBK size down. ?
You still need to match 64/69mm valve related components. Doesn't' matter what bore size. Stock heads may work on smaller bores and not larger because of compression, not due to valve length.
@@49ccscoot so even though I opt to run my stock head possibly I should take off the cover and take a peak to confirm valve length even though I'm not planning on changing the valves and just changing the jug part? Only ask because I see basic "jug" BBk and then full BBK with new heads and jugs. Again plan was just going 39-47cc piston size
@@DarkHorseModz If you're using the stock head, it doesn't' matter, but you mentioned a kit with a head too. Then it would matter.