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- เผยแพร่เมื่อ 30 เม.ย. 2016
- Information about piston to valve (P2V) clearance. What is P2V clearance? What affects it? How can piston to valve clearance be changed?
The information in this video is relevant to many four-stroke engines, with specifications intended for small engines like scooters and motorcycles. Larger engines, like V8s will generally use larger clearances, for example 0.080" intake and 0.100" exhaust, but the other information should be useful for most applications.
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thanks man.. seriously, this is nice of you to post secrets of the pros
Accurate and supportive information relayed here!
Have been in valve clearance thingy from a week since i open my bike head for the first time. You video cleared two of the major questions for me Crystal clear. Why we need to adjust valve clearance and why the piston should be should be inserted in the right way ( which side should be up and and which side should be down on the exhaust side.
SO thanks alot
I'm glad it helped!
Now i see why is better adjust valves with Stop engine, we can damage the piston or Valves while we adjust it.. Good explanation
thanks a lot for sharing this info
my honda xr 150L intake tappet valve clearance is .08mm and exhaust is .12mm(standard).. i brought it back to my dealer for a tune up at 12k km odo. they adjust the intake to 0.10mm and ex 0.12mm . anny disadvantage for not following the standard clearance?
Very nice you inspired me to teach
my honda xr 150L intake tappet valve clearance is .08mm and exhaust is .12mm(standard).. i brought it back to my dealer for a tune up at 12k km odo. they adjust the intake to 0.10mm and ex 0.12mm . any this adavantages for not following the standard clearance?
If the dealer told you this, then I'd assume they have a reason... or they updated specs... or just got the wrong specs I guess. Could be that the manufacturer or dealer believes it's better to open the valve 0.02mm less for some reason (P2V clearance or changes the way the cam works just a tiny bit) or they've found stock settings to be too tight and allow the intake valve to hang open in some cases. The best bet would be to ask them and see what they say.
@@49ccscoot Honda philippines just answered my message .. they explained something about the tolerance .
I can't understand English but gasket solution working good
Very good brother thanks
Do you recommend a performance cam for my 200cc push rod engine? I am planning to upgrade my motorcycle, but I actually afraid to destroy the engine. Pls help me, If you recommend performance cam, what is the best size? The available in the market here in the Philippines is 6.5, 6.8, 7, and 7.2, pls help me
I don't know enough about those engines to give you any recommendation. It would be better off to find someone that is familiar with the engine type that you have.
shouldn't it be 0.005" instead of 0.050"? I'm just learning this stuff and I've seen 0.005 everywhere else..
Definitely not. We aren't talking about valve lash, like setting the gap between your rockers and the cam. That would more commonly be around 0.005". 0.005" piston to valve clearance will leave you close to disaster.
Me 0.050
How would set zero lash on all valves in a bike with shim type valve adjustment? Would i need to buy thicker shims and insall them under the buckets just for this clay test?
You'd set zero lash just like pretty much any other lash setting that you were after on a shimmed bucket. Measure the clearance and get shims with the appropriate thickness to adjust that clearance to 0.
@@49ccscoot i see, lots of bloody work then..thanks for seift reply
@@Adikxx Unfortunately all of this kind of work gets pretty tedious. If you don't want to risk it, you have to spend the time. Some people just check 1 cylinder.
bro i have decarbonized my engine head and changed both valves, also cleaned carburator. but now iam not getting mileage. there is no sound from engine and it starts and runs smoothly the only issue is iam not getting mileage as i used to get. the mechanic have even tuned the carburator. i dont know whats the issue. pls help. honda unicorn 2013. 45000+ kilometrs. current mileage is like 38 km below . i used to get around 50 before. pls answer if u know.
1 really simple idea is to make sure nothing is leaking. A small leak could change observed fuel mileage significantly. Fittings, hoses, float height.
You say 45,000km... had you seen it doing 50km recently? Sometimes people use old data as a reference, but it could have been steadily declining.
Engine compression check wouldn't be a bad idea. Could be something not engine related, like low tire pressure, CVT or gearbox issue.
Sir... id like to ask i change my piston frm 52mm change to 57mm piston is thier any problem if my cylinder head chamber is stil original or should i bigger my chamber into 57mm size... thanks you sir more power
It's different in each circumstance because all parts are not made the same. One cylinder kit may have the piston below deck and create lower compression and larger squish clearance. Another may put the piston level with deck for high compression and tight clearance. A cranking compression test would tell you a bit. Squish clearance check would be good. At least rotate the engine over by hand before you ever try to start it, to be sure there is no contact of the piston and valves. Valve clearance check if you want to be more precise. Calculating compression ratio is good if you're in doubt.
For gy6 50cc, valve adjust suction how many mm. How many mm of exhaust. must be
0.065-0.07mm or 0.0025-0.003".
Good
Do you know what are the safe recommendations for PTV clearance on bike engines bud? Just finished my build and i'm 2mm of clearance both on intake and exhaust valves. Hope that's safe enough..
That should be OK. I have seen people say you need a little more than that on the ex side of some larger MC engines. Wouldn't hurt to do a search and see if you can find info specific to what you're working on to be safe.
How many degrees is the base of the exhaust valve open and closed? and how much is the valve open and closed?
I mean you are basically how many degrees the two valves open
Depends which engine and what cam is in it. If it's a Chinese engine like a GY6 or 139QMB, then I'm not even sure that it would match up on a large scale.
@@49ccscoot yes thank you for the answer, maybe it takes time to install the camshaft to understand how it is😊😊😊
Very helpful
What happen if exhaust valve is a bit loos or a bit tight, pls clear the both situations.
Loose will clatter and can reduce open duration. Tight can hold the valve open so you lose compression.
I just did a valve adjustment and now I have oil spewing out of inbetween the rocker arms, any ideas what's happened and what I need to do to fix it please?
I'm thinking you may just be seeing how the top end is oiled and that's a foreign sight if you aren't used to seeing the engine working with the valve cover off.
@@49ccscoot it spat quite a lot of oil out which made me panic a bit,
First time I adjusted there was a fair bit of tapping, so I stopped and re adjusted the valves again, started her up and a big splash of oil came out
The valves were really tight before I adjusted them as well, wondering if adjusting them has caused damage that was there to show up now or something?
Does the crankcase cover need to be on to start the engine?
@@clive00rennison The cover should be on when the engine is running or you're going to have oil spurting out.
@@49ccscoot ok, will put it back on in the morning and start her up and hopefully it doesn't spurt any more out 🤞🏾thanks for the help
So I've taken it apart again and replaced both top and bottom end gaskets and it's still puking oil everywhere, it kinda looks like it's leaking from the groove in the rocker arms bit?? Any ideas?
are there any spring less valves???
These springs are pretty much the standard. Really high end stuff (like MotoGP) may be using pneumatic setups. Ducati uses desmodromic valves.
is it true that i get more power from my engine if i make the valve clearance lesser? because i have a really thick head gasket in my gy6 engine now so i know for sure that the clearance is a lot more that you sayd it should be in the video. i have a 72cc with a9 cam you think it is worth the efford? thanks .
Just to be clearn, many call valve clearance the valve lash... what you do when you adjust the valves. In that case, lots of lash settings can change performance to some small degree, but given the topic of the video I don't think that's what you're asking about.
Changing piston to valve clearance alone, I don't think will do much for you. Tightening up the squish, or the distance between the head and cylinder in general, raises compression if no other changes are made and that may improve performance. Tight squish clearances also help to prevent detonation. If you want the most from your engine, it's worth the effort to at least find out what kind of clearances you have and if they can be easily changed. It's also good to figure out your compression ratio, or at least a cranking compression figure (compression tester) so you have an idea if you even should push it higher.
90GTVert thanks for the response I meant the piston to head space. I have a 72cc glixal kit and it came with a really thick head gasket so I think its a good thing trying to tighten the squish its pretty fast already but I think the engine has more potential.
Sir good morning I'm Filipino may I ask if there is a advance cam...to motorcycle ? Tnx
Depends on the motorcycle, but cams can be advanced.
Tnx sir may motorcycle is Suzuki raider 150 DOHC is it possible the cam to advance?
Sir can I request a video from you how to advance cams?
@@arielmelon8413 You would need to see if anyone makes an adjustable cam gear for your application. That or cams with an adjustable gear already installed. Just moving it a tooth is not a good option and can move the cam way too much. You can see info about me using an adjustable gear on a GY6 150 here : 49ccscoot.proboards.com/post/230617/thread
thks man
Meli metar kitna hoga
Why more clearance to exhaust side?
The exhaust valve is chased up the bore and also the exhaust side runs the hottest and clearance is more likely to change from heat related issues.
I dont think modifying the piston can help, it can cause slight vibration to the engine.
I wouldn't go grinding away on a balanced rotating assembly. For what I work on, it's not generally an issue.