So ive been riding my 1992 timberwolf 250 and all the while trying to get the carb adjusted right. ive been thru it 3 times and im confident nothing is clogged and I know the starting settings, but once i begin to adjust from there i get little improvement, The problems im having is getting it to want to run smoothly off choke and it wants to just bog and die if i punch the throttle alot of times, but if i dont hit the throttle as quick it does fine. With the choke off it will run okay, it will back fire out the exhaust when you rev it and let off the throttle and also with the choke off it doesnt want to hold a good idle as it will sputter and die unless you crank the idle speed way up, but then its too high. However, if you pull the choke to about half alot of the problems will clear up. it will idle better lower, it rarely if ever back fires, and the bogging and dying isnt as bad either, but its still present.

Intake boot is good, other boots are good, fresh and oiled air filter. new plug gaped correctly . I assume good compression( my checker doesn't have the right fittings) doesn't smoke. and it felt good when i put my finger over it and it shot it right off,
The valves may need adjusting as their alittle tinky , but not too bad. Found no slack in my timing chain. Now for the questionable things, Ive noticed the spark doesn't look that bright. but its there and consistent, How would i go about confirming its quality?.
The other bad thing is that the muffler is pretty shot. holes and rust all in it. looks like someone tried to patch it but their welding made it worse im sure. One of the confusing things is if i pull the plug after some riding its not fouled, but definitely looks to have been running rich with a black coating and fuel smell, but what i dont get is i tried to lean the mixture by adjusting the needle in the slide, but it would hardly run on the 5 setting. 4 setting and it would run okay, but needed to be on some choke. 3rd setting and it would run more acceptable off the choke as it could idle and so forth when warmed up. I havent gone any richer on the needle than the 3rd setting. But all in all what im finding i that if i rich it up it will run better(still not right, but much better) But then the plug looks and smells like it was run too rich. Right now my pilot jet is at 1 1/4 turns and my float is good to my eye about level and the needle is on the 3rd setting. could it have to do with the very leaky/blown muffler? or could a weak spark cause these issues?

as it sets its ride-able. backfires occasionally and the bogging issue still shows up sometimes. but usually only if you punch it from a dead stop or punch it in say 3rd from a slow roll. other than that it feels strong. itll pull the front wheels up pretty easy in 1st and sometimes 2nd and will climb hills fine in 1st and 2nd from a dead stop, but any higher gears and youll need to have some initial speed.

 

First off, are you absolutely certain the intake manifold and gaskets are perfect? If so, was the fault there before you fitted the new plug, as a new plug doesn't mean a good one. Fit another anyway. Check the charge rate, if the regulator is putting more than 15v into the battery, you will get the ignition system playing up. When you checked the plug and found it sooty, had you been riding with the choke partly on? It is possible a slightly richer idle setting, and leaner main jet setting, would work better.

You can get a tool to check the gap the spark will jump, Briggs & Stratton's is not expensive, but I have worked on small engines for the last 20 years without feeling the need for one.

"and will climb hills fine in 1st and 2nd from a dead stop, but any higher gears and youll need to have some initial speed." Always set off in first gear, the only way to set off in higher gears is to slip the clutch, which does the shoes no good at all.

 

try shutting your gas off after starting. I had a wheeler that ran really hard because my float was adjusted just a little too high and when I shut the gas off it cleared up.

 

Yeah im fairly sure. I did a visual inspection and shot some carb cleaner around to find a leak and got no response. And yes the sooty plug has appeared after some run time with partial choke. But again it runs much smoother with some choke.

And to be honest im not 100% sure on the plug difference. It still had its backfire before the plug change, but i dont remember if it was having an idle issue. It did bog still. And i know of the tool your talking about i have a spark checker and i could make one of those gap jumping ones.

How would i rich the idle and not the main on one of these? And would the blown out muffler cause these problems?

And yeah i know its not supposed to start off in 3rd on hills. That is asking too much of it. But i did notice on the one ride i took on the mtn if you shifted up to 3rd on a hill/incline even with some built up speed it would try to bog and die occasionally.

And i hadn't tried shutting off the gas yet, but i can see if it does anything.

 

Ben...when you say clean...that can mean different things to different people. Your idle issues sound like a clogged pilot (idle) jet because you mention it idles better with the choke on...all the choke circuit does is to richen the overall mixture. The pilot jet is often next to the main jet but set deep inside. It's often difficult to remove and is often not cleaned properly. If not done already, I'd pull that jet and ensure you can see through the ity-bity holes it has.


You said you know the starting settings, but did you verify they are stock settings? I'd also verify the jets are stock as that's usually the best baseline to start from.


You may have a combination of issues that is making the tuning difficult...a clogged pilot jet and oversized main or improper needle jet/position can make it tough to get it running crisp...

 

I have taken that jet out as well and i can see thru it clearly. Ive blown thru all the passages and im fairly confident theres no blockage, but maybe there is one holding something up.

Also to the earlier question about voltage the highest i read was 14.5v when revving the atv.

Too my knowledge from researching stock settings are. 1 1/4 turns out on the pilot. 4th position on the needle jet. And adjust the idle as needed. And the float should be something like 23mm from the gasket surface. Aka level.

Things tend to improve as the quad warms up too. I took some videos of its issues and ill post them here shortly.

 

Here are some videos showing what im talking about,

 

Most yamahas after 1988 are 2 turns out on the air fuel screw. And if the carb was really dirty you need to use a wire from a wire brush in the holes on the jet they can look clean and not be clean you have the main shaft and than the side holes the wire will free junk up in all of them holes.

 

another thing is your air screw in there properly? have the screw than spring than washer than o ring

 

So...the A/F screw is not the pilot jet...so just ensure everything is as clean as you can get it. Generally, the A/F baseline is 2 to 2.5 turns out from lightly seated...


I'm curious what your compression is...do you have access to a tester? They are fairly cheap at a local auto parts store...under load, a low compression motor will act like yours...just something else to think about...I say compression because it revs fine with no load (neutral), but dies when you give it throttle under load (in gear)...just don't want you chasing a phantom...