Hello everyone.
I’m new to all this (the website) but I’m hoping someone can PLEASE HELP ME.

From what I’ve seen this lack of power seems to be a common issue but I’ve yet to find a definite answer as to why.

I bought a 2003 Yamaha Wolverine a few months ago and after fixing a few things, like clutches to get it moving, I realized that it only tops out to about 26 mph.
I’ve spent months trying to figure out what it could be and I’ve called all the friends I know. I don’t know what’s wrong with this bike.
I’ve given up for the time being but I’m sure soon I’ll try again.

let me tell you about the atv:
it has an hmf high flow exhaust.
warrior carb
And I believe a high compression piston
i should also mention that there is evidence that people have been inside this thing and from what I could see from taking the clutch cover off is that they were very sloppy.
the Bike also smokes a little when revving it high.
the bike also runs hot (my legs get real hot when riding it)
the neutral position sensor is bad, it goes into reverse instead of going into neutral without even touching the switch.
the electrical seems sloppy so it may be a simple electrical issue.
there is an issue with Yamahas where the handle bar electric switches (or parking brake) can stop the bike from running, I think has been bypassed already bc all the electrical to the handlebars is gone except the starter.
also bad starter solenoid but don’t think it’s related.

So I replaced the carb.
checked the valve lashings
compression is 150 psi (manual says 120 is where it should be, my guess is there is a high compression piston on it).
fixed an exhaust leak.
I jetted the main jet several times with no top speed gains. I only ever lost top speed never gained it. I don’t have it right but I went from lean to rich and still no increase in top speed.
I have not touched the needle valve or pilot jet but don’t think those would add a 50% boost in power anyways.
also I tried air box on, off, air filter (stock) on, off, I tried plugging the exhaust and running air box closed.
I tried all the different combos I could think of.
i went from a 145 jet to a 155 jet to a 170 jet and I’m telling you I had no top speed increase and almost no decrease (like maybe 2 mph) but I could feel a difference in how it ran.

I honestly don’t think it’s anything to do with the carb. I tried two carbs on it. The one currently on it is from Amazon so I know not the best but seems ok. Also I didn’t put all that crap on the bike. I’m just the guy who bought it and is trying to make it run well. My goal is if it can hit ~50mph or high 40s I’m happy (that’s a little below stock speed). I’m just trying to get it to run well and feel a little burnt out.
Plugging the exhaust helped a little but I got scared I’d do some damage plugging it more so I stopped when I ran out of gas and thought I blew something…
hahaha had to push it back to my house.

only once I got it to go above 30mph and it hit like 40mph.
the way I got it to hit that was by running it on a trail for like 2 hours, it got hot for sure (no oil light tho), and then at the end when I was going open throttle it actually started climbing in mph!
it may have been my gps app that I used being faulty but I got it to do that a few times in a row so I think it’s legit.
I am baffled.

also on that trail the bike was so weak that it couldn’t even make it up a 1 foot dirt hill. I had to push it up the ramps to my truck. Now after some work, it can make it over the ramps no issue and revs high and stuff just doesn’t have top speed!!!
losing my mind no lie.

I honestly have no idea what’s wrong. Maybe someone tampered with something? The guy I bought it from said he had it for his 9 year old daughter so maybe he put a rev limiter or something? I’m hoping some Yamaha wizards could help me out. I’m thinking it’s got to be something simple stopping it from going.
if it’s a bottom end issue I’ll probably just sell the bike.
it’s really cool cause i know wolverines are unique and fast and it has a warn 424 converter on it! Those things are crazy rare! Warn doesn’t even make em or parts for em anymore!

thank you to everyone who reads this.
im praying someone wise can tell me what’s wrong!
God Bless You All!

 

Could it be a bad CDI?

 

Clogged exhuast pipe…

 

Engines run hot if the mixture is weak. I also had a Kawasaki 300 that would turn the exhaust pipe cherry red within a couple of minutes of running. That turned out to be the exhaust cam worn and not opening the valve much. Valve clearance wasn't far out, as that is set where the cam isn't lifting. Trouble is, with all the non standard parts, you have a job knowing what is right. Are you sure a clutch isn't slipping? I can tell that right away, but I guess you have to know what it does feel like. The inability to climb hills would point to this, it would be revving away and not climbing, rather than the engine loosing revs.

 

I just changed the clutch pads and the centrifugal clutch. They feel fine. As far as a clogged exhaust, I don’t think so because it feels like there is too much exhaust flow if anything.

thanks for the help I honestly don’t know what the issue could be. I just hope it’s not the bottom end.

 

Then, I would check for worn cam, as merryman suggested… I think the valve lashing is irrevelent on a worn cam or maybe cam timing off…
stock sprockets?

 

Oh boy. I’ve never worked on cams before and so I don’t know much about them. They are bottom end huh? Any easy way to check them?

 

No, as "top end" as you can get, as the cam sits in the top of the cylinder head. A rough idea of whether it is a cam worn is to take the valve covers off and see if the cam presses the inlet and exhaust valves down by roughly the same amount, as you turn the engine by hand. It is worth checking valve timing before delving deeper, but to be sure the cam is OK you take it out, which means removing it from the cam sprocket and chain, which can be a bit of a pain. Get the workshop manual before doing any work on an engine. You need it for measuring the cam lobes etc, and it points out things you need to get right when removing and re-assembling.

 

Can you tell me where I can find such a manual? Any resources you can give to help me (like a video or something)?

i have a few questions to better understand the situation:
Like I mentioned, it gained power when it warmed up once.
It also runs hot and has higher than normal compression.
Are these symptoms of a bad cam?
just trying to narrow it down before I strip it bc I’m honestly considering if it’s worth the work or to just sell it. I do want to see it run well though.


im gonna have the bike get checked out by a buddy of mine then I may take it apart after he sees it.

thank you very much for your help btw!

 

When I wrote about the Kawasaki running hot and it being a bad cam, I was just suggesting that this can be a cause of overheating and low power. Doubt if it would run right at all, if the cam is shot though. Other causes are a weak mixture etc. Probably best to let your buddy take a look, if he genuinely knows about small engines and how to fix them. Regarding manuals, you may be able to find a used copy of the genuine Yamaha manual on EBay etc, or a .pdf copy of it. Free .pdfs of most manuals are available on-line but you never know for certain if the site is genuine, or a malware site. Clymer and Haynes, aftermarket manuals are also available for most models, but may not be quite as detailed as to cam size limits etc.