Honda VT750 Shadow NIGHTMARE Diagnosis - Part 1
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- เผยแพร่เมื่อ 17 มี.ค. 2023
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In this video I wanted to let you in on what it looks like to go through a little more challenging diagnosis when it comes to a slightly modified carbureted bike.
When dealing with bikes over 10 years old there are many factors that can come into play when trying to pinpoint a problem. Especially when so many people have had their hands on the bike.
Is it carb related? Has it been jetted properly for the modifications? Is the ignition system failing us and giving us mixed signals?
Let's find out!
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The diagnostic process is in my opinion one of the most misunderstood parts of mechanical repair. Probably the most important, as you can't fix a problem without it except by luck - and it can get very expensive before you manage to find that "luck." Even if I can't do the actual work myself, it really helps to know I'm not being snowed by a disreputable workshop with a parts cannon.
PS: It goes to show there's no substitute for an actual diagnosis. When I first heard it breaking up, I thought it sounded like an ignition issue. Never trust instinct - logic always wins. 👍
Loving the content on this channel, seeing what goes on when you took all that apart was amazing.
And now my choke is staying in place with your choke adjustment🎉 genius! Thanks mate
That was an absolutely excellent video and really enjoyed watching you go through the process of troubleshooting and diagnosing the issues. Obviously the rust and sediment in the fuel plays a big role in all this however I'm curious to see what "surprise" there's going to be towards the end of fixing this bike to run correctly. Very well done Cody - thanks so much for putting these videos together, great job brother! God Bless!
Plugs say lean.
1-2 plugs not fully seated.
1 plug squashed, probably not firing, however the other plug will be.
Fuel supply looks restricted but we haven't tested fuel flow rate or fuel pressure. Perhaps there's a tester for that? But rusty fuel tank, lots of filters. Possibly the pump is damaged or underperforming. I want to test flow rate and pressure to the carb.
Symptoms only happen when extra fuel and air and spark power are required together. I'm guessing a weak spark would cause wetter plugs, whereas we are seeing all fuel burnt.
So too much air, too little fuel, something like that.
Love this video man now I have an idea what could go wrong with my bike. Thank you bro!
Fantastic video. I enjoy watching. I always learn something.
Glad you enjoyed it! Thanks for hanging about 🤙🏻
Wow, a lot going on in there. Can’t wait to watch part two.😮
I just found your channel, I have ridden with my friends' same 2001 Honda Shadow ACE 750 and heard / seen the problems, spitting sputtering and smoke, now I am about to delve into finding the problems with it. look forward to reviewing your vids...
Such a Great video brother !!! keep up the great work !!! Cheers from new york !
Thanks man! 🤙🏻
I appreciate your channel so much! This particular video makes me glad I held out for a stock Shadow to purchase. All I had to do was replace the carb boot and adjust the mixture to correct a slight stumble, otherwise none of this mess. Thanks for sharing, stay well from the Morris IL area!
For the very reasons we see in this video, every time I bought a used bike I always by one that’s completely stock. A lot of home motorcycle mechanics really suck at it. (And you find out as soon as you remove the oil drain bolt and find that it is cranked down to 900 ft/lbs). You were right to hold out for an unmolested bike.
Obviously was starving for fuel with the clogged petcock screen. Clean out the tank as best you can, get new petcock along with the screen and spray through as many of the carb passages with carb cleaner as much as you can, if idle, pilot and main jets appear clear, reuse, replace the fuel lines (very cheap) and take out that extra fuel filter after the pump, button it up and you should be good. Right?
Nicely done!
I enjoyed the video thanks
First time on your channel. Old bike mechanic and enthusiast. Today I agree on your thoughts except first thing I'd check is the fuel itself for contamination, quality. Double check crabs for blockage . Then after your other checks is the ignition quality and and valve adjustment doesn't hurt . Replace plugs with new ones and run and ride and recheck for jetting again.
Im an inexperienced tech so seeing your process was very helpful. Thanks! 🙏 Also I'm thinking perhaps check flow of the fuel pump now it probably has crud in it? Honda might list a certain volume of fuel per so many seconds etc...
Good Job!
I think it's a number of factors. I am a tech by the way as well. All those filters would be causing a restriction for sure especially the smaller ones being completely blocked.
The air going in is probably too much for those carbs to handle. I would cover that stupid air filter with some layers of perforated tissues for testing to try to get less air into the system.
The carb may need a complete dismantle for cleaning as well. Man can be so many things lol. Sometimes the spark plugs look good and can actually be faulty. Ignition coils blahh blahhh so many things.
You are not wrong with any of that logic! We think much alike! 👌🏻👌🏻
Mate I have very much appreciated your words and mental process on a few repairs thus far! I am betting that the VT750 has a carb slide problem, likely exacerbated by the crazy intake. Those carbs have been meddled with- are the slide channels fresh and clean? I would put my money on a carb replacement combined with stock intake. I'm all eyes to see the results here- good luck with the bastard!
Good methodical troubleshooting. After you clean/change the filters, I would replace the fuel lines. Then do a flow volume & pressure test on the fuel pump. Verify the carbs & jets are good. Also the intake boots need a good looking over while the carbs are out. Bore scope the cylinders, & intake. maybe exhaust but pipes would have to be removed.. I don't like the spark plug being hit. Once the fuel is up to par, the compression, valve lash & timing would be my next check. Weak valve spring(s) come to mind also Electrical would be the last thing on my list
As a proud owner of a 98 Shadow VT750 C3, I would 1. drain the tank and refinish the inside to remove rust, 2. replace the fuel filter and get rid of the other filter, and 3. flush out all fuel line hoses. 3. most likely have to do the carbs and jets also. .
Hypothesis: rust enter the fuel system via the gas tank and contaminated the who system including jets.
Great video! I noticed you had silicone spray on the bench and it moved in the different shots. What did you use the silicone spray on?
Fuel restriction sounds like a good reason, but from the test ride it seems that problems are only on higher RPMs AND on idle (throttle off), at least that's what I noticed from the video. If that's really the case and not just my impression from the video, it would mean that there is enough fuel supplied during the open throttle, so fuel line flow rate is OK. It would then point out to the idle circuit in the carbs, maybe some gunk built up there, before the filters were even installed?
My second guess would be that the mixture may not be set up correctly, you improved the mount on the air filter, which can possibly lead to smaller air intake now and richer mixture. But on the other hand, I am not sure if that would caused the problems during the test ride.
BTW I am a super beginner, started working on my bike last year. Your videos were super helpful to work out a logical diagnosis process, I learned a lot from them!
Im looking at a VT750C2 this afternoon. My experience is with my 1979 Limited Edition 750. I did not realize it was going to be shaft and liquid cooled. I have a lot to learn just to check the bike out later today. Thanks for this vid - Per Question - The external filters look new where an existing issue of crude exists from the tank, and eventually to the carbs. Hence carb was contaminated before the new externals were added -
My best guess would be dismantling all the carbs and cleaning them perfectly. Given the amount of dirt in the last filter and the relatively clean bowl, a cleaning has been done. But it was not a full cleaning otherwise the filters would be clean too.
Then of course clean tank, put a new set of filters ONLY where they are supposed to be, check floats level, check fuel flow. Give it another try.
Deductive reasoning, the driving force behind all good mechanics. My initial thought was starving for fuel...
Mine too!! 👌🏻
The screen on the fuel pickup isn't really a filter. It's a fuel pickup screen for chunks
next step is to clean the tank-replace seat screens and petcock with new screen. consolidate fuel filters to one filter. Reassemble and test drive
Valve clearance or sticking valve? Or bad earth or electrical connection? Are we allowed 2 guesses?
I would get ready of most of the filters and let the gas flow a little better
Cody, you have a digital Dsynch2. Whay use stone age vacuum gauge? Digital tool shows a perfect intake port diagnostics...
That sparkplug!
Comparing low speed test ride to high RPM the first thing that is indicated is fuel starvation. The carbs are in spec and are to be blown out or boiled to clean. Fuel pump volume check with hose and filter cleaned up to stock configuration. If no solution at road test then a low voltage ignition or intermittent spark at high RPM. Good luck I hate duel carb set ups.
Worth checking the flow rate of the pump ?
Hi Cody, Love a good diag.
My 07 shadow vt750c2 makes a "whirring" noise only during engine braking. Would this be considered normal for thid model ?
You sure make the carb removal part look easy. (It's not)
Do a thousand of them and you won’t feel the same way! 😂
@@TheMotorcycleMD Yes, I'm sure that's true, I have an 05 shadow 750 with the engine popping a little at idle a little more on deceleration. But overall it's manageable. I'm looking forward to part 2. Greetings from SW FL.
Carb removal is a pain on this!
@@DragonSol42 I have the same bike , try this remove both drain screws and flush with carb/brake clean. It helped me
Well since you seem to be hinting that the extra filter and all that crud isn’t the problem, which would have been my guess, and that the plugs show a lean condition despite the extra jetting… I’m going with floats set too low?
Air fuel mix, I think. Off the bat when you say bogging. Good luck Great vids.
👌🏻👌🏻👌🏻👌🏻
Aftermarket mufflers and need a bit of a carb adjustment but I've never owned a Shadow. Harley's yes. Vintage Hondas..yes. 2006 shadow aero 750 ....no...ha. Not bad but a bit of tweak needed.
Vaccumhose from rear cylinder to petcock, If leaked the engine runs bad like that, or maybe too lean
because of aftermarket intake and exhaust, maybe earlier models do not have that hose connection
Exact. Vacuum petcock valves appeared on Shadow Aero, and this is previous Shadow ACE model.
I'm having trouble with my gl 81 1100 Gold Wing. But it's coming down to eather it's the cable from the starter has caroaded or I'm going to have to pull the starter and clean it and put it back together. I did a bunch of work to it and then it got stolen. It's been 3 years but I tracked it down. But when I did get it back wires were cut and rust in the tank. I'm using a starter relay from a Ford 150. I got a new battery but I only had a one amp charger. I'm having problems getting a deep cell charge. The charger says it's charged at 12.88 but I know it's not. How do I get a deep cell charge now? Should I put it on 2amp charge and watch it with the multi meter.
Awesome video I'm currently working on a 2002 honda shadow 750 and i am stumped on what is wrong with it I've just about changed everything and it still cuts out at high throttle
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Maybe a contact is lost at battery terminals or INSIDE the battery (due to vibration at high rpm). Sometimes, a terminal has a crack inside and it may randomly cut out. Try a different battery. Also, instant cut out of both cylinders instead of slow dying or shutting off one cylinder suggests that it is 1) an electrical problem and 2) it is somewhere closer to the battery rather than plugs.
Question .. following your videos .. ty for that btw .. i found that my Airfuel mixture screw is not "deep" in the carb like this bike .. you know if its normal to mod it so its level with the face of the carb ? .. hope you understand what i meen :) its a 2000 Shadow ace and its out 3 1/4 :)
I have the same problem on my bike.
There are not good mechanics in my city.
Open exhausts sound cool but make your bike run like crap. I bought a Shadow VT1100 with an open exhaust and one of the first things I did was change it back to stock. Tuning an open exhaust sucks.
Ebay stock parts, its a cruiser not a rocket. In stockish form it should be dependable.
I see a lot of people change the exhaust, and the bike runs badly. Doesn't the carb need adjustment after an exhaust change.
It sure does!
That’s what mine dose Boggs out, vt600 done fuel pump, cleaned carb, reset needles, still happens. 😢
when do we get part 2?
Where’s part two?! I hate suspense !
My money is on a bad connection to the fuel pump!
I'd be happy to purchase vids on my 2006 Honda Shadow 750 aero, How do I get to be a paid member for my particular bike?
Where can I get that spark plug removing tool you used in 10:52 ??
Hello, I actually have the exact same problem on the exact same bike accept I have velocity stacks and drag pipes. It had blow by in the cylinder quite some time ago so I had to replace piston rings as well as valves and valve springs among many other things. I’ve gotten it running a few times and tracked a problem back to the computer. The wire granting proper power to the ignition coils had a terrible connection at the point between the computer connector. So far I’ve replaced the fuel pump and new spark plugs so im thinking im narrowed down to tuning but still having some trouble. Im set up with 45 and 145 all around for the carb set up and am unsure what jets to try now.
I’ve also fixed that connection, new clutch pads, all new fluids, and I noticed the different sizes jetting for stock and was wondering since I can’t get the bike to actually ride what jets I should shoot for
My 1986 Honda vt500c drops to one cylinder after riding for about 2 miles and then kicks back to full power after a mile or two. It does this every single time but varies depending on how warm or cold the ambient temperature is (stays at one cylinder longer when colder). I'm in the process of diagnosing it and put a new CDI box in it because I was sure that was my problem. Has anyone else ever had this symptom on a bike? It's almost comical that it cuts out and back in at nearly the same point down the road, I'm always putting through this same little town on one cylinder 😂
Check color of sparkplugs, that will tell you a lot
My shadow has the same problem since I bought it about a month ago. Still don’t know what it is
125/130 mains is too small for a shadow 750 with opened up intake and exhaust although with all that garbage in the carbs having bigger jets wouldn't really help anyway, once the carbs are clean and flowing with that intake and exhaust an increase in main jet sizes to 135/140 should be pretty close......
I thinks is "all of the above!"
Dirty fuel has gotten the best of me twice by now. Sometimes it's best not to over-complicate
I have a02 vstar 1100 has same issues, p o put a hyper charger on it shotguns pipes, so I rejected the carp it's alittle better but stil thare. ?
Great question! You will enjoy next weeks video as well!
I reject carps, too. I do accept salmon, though.
So which honda shadow is the best model in the family
For someone like me I'm still doing my research until I can afford one but I did hear good things about Honda shadow but not sure which model I should aim for
Stock ACE looks the coolest)
@@ilyaanry yes its a beautiful model kinda close to Indian heritage version
But isn't a bit heavy for someone like me who never rode a bike?
@@K-G-S_66 sure, it's not. It has a low center of gravity and low seat height, rides like a bicycle once you start moving. It was also my first bike, by the way. Never had problems. But, once you get it, train your skills (it applies to any bike, of course)
At the beginning of the video I'm thinking, "Bring the bike back to stock and then move forward." Meaning, don't just go after what you think it is based on the symptoms, first off, make sure everything is working as it should. While doing that, you might find the culprit.
Bingo! The bike has been molested by a rank amateur with no consideration for what is right!
8:45. Possibly the reason for two fuel filters. Previously rusted tank.
22:15 Bingo on the rusted tank!
24:00 This is why so many mechanics don't want to work on old bikes.
Let's see if part 2 says, "Perform maintenance to all the bike's systems and bring them back to factory specs." That's the basic common sense and logic approach.
Rap the hand grips with tape on inside, stops sliding grips
I'm betting on the gas tank vent line being clogged.
👍🏻
The easiest and most sure way to fix a bike like this is to get a service manual and go through parts that are not OEM, and change it back to OEM.
That is why I normally stay away from modded bikes or I get them with a very low offer.
BTW, the fuel pump would not really add resistance. It will actually add more pressure, thus removing some of the friction.
Valve
Timing and air
= 10 horsepower
I would have to say contaminated
Fuel system
I have some inklings what the problem might be, but I'm almost certain the owner is over 50 🤣
Another victim of E10. I believe