YZ426F Problems?

[deerman2701]

I kno its a warrior forum but hey il see if u guys can help me and my buddy out...

So my buddy has had his 426 since last year and recently it is havin some problems..

ive checked the timing, cleand the carb, jetted, checked valve clearences, fluid levels.


okay so just recenty his 426 has been getting real hot real fast, maybe its normal but the header and engine gets too hot to touch within like 3 min.

also the idle seems to be irratic, ie it idles fine one min then when he slows down it will be too low and stall his bike...

and lastly the bike just randomly cuts out and dies... then its hard to start for a little bit. and just doesnt run right?

any ideas?

im trying to get it fixed for saturday cause i wanna take him to wellsville!

 

[jgray44]

does the head pipe turn red right by the head? could be running way lean, pull the plug again and check it out

 

[bryanquad]

I kno its a warrior forum but hey il see if u guys can help me and my buddy out...

So my buddy has had his 426 since last year and recently it is havin some problems..

ive checked the timing, cleand the carb, jetted, checked valve clearences, fluid levels.


okay so just recenty his 426 has been getting real hot real fast, maybe its normal but the header and engine gets too hot to touch within like 3 min.

also the idle seems to be irratic, ie it idles fine one min then when he slows down it will be too low and stall his bike...

and lastly the bike just randomly cuts out and dies... then its hard to start for a little bit. and just doesnt run right?

any ideas?

im trying to get it fixed for saturday cause i wanna take him to wellsville!

the pipe is going to get hot like that it should b red when you r on it i have that motor in my quad and the pipe glows red its fine i would say that it has sum thing to do with your valves like you have one that is cupped is it hard to start ... how hot is the motor getting do you know

 

[deerman2701]

Personay I don't think it's any hotter than it's suppose to be he keeps saying it is though.

He said it only started up after he got on it in fifth gear pinned.

If a valve was cupped wouldn't I have 0 clearance on a valve?

 

[bryanquad]

Personay I don't think it's any hotter than it's suppose to be he keeps saying it is though.

He said it only started up after he got on it in fifth gear pinned.

If a valve was cupped wouldn't I have 0 clearance on a valve?

yes is the pads good r they wore at all r is the plunger clod r hot start damaged at all r your valve seat is leaking just a lil bit r look at the crab boot to see if it has any damage

 

[duneracerweston]

Id do a plug chop on it to check jetting just to make sure because no motor should glow the pipe in 3 min idc what it is check jetting and check for watter in the fuel that will complete ly screw a bikes running quality for sure

 

[deerman2701]

the plug was pulled and its blacker than all hell...

 

[duneracerweston]

Sand blast it and go again that plug may hav had tomuch crap on it

 

[deerman2701]

so i took the carb off looked at the jets and the stock sizes are pilot is 42 stock and main is 162 stock..

the bike has a 48 pilot in it and a 162 main...

should i down the pilot to a 45 and main to a 168? since it has the slip on and hotcams? it runs cooler with the choke on btw. and pops a lot on decel

 

[jasonp]

so i took the carb off looked at the jets and the stock sizes are pilot is 42 stock and main is 162 stock..

the bike has a 48 pilot in it and a 162 main...

should i down the pilot to a 45 and main to a 168? since it has the slip on and hotcams? it runs cooler with the choke on btw. and pops a lot on decel

Sounds to me like main is jetting rich and to LEAN on the pilot/fuel screw air jet.. or plugged.

Popping under decel is a sign of lean condition on pilot jet or fuel screw, air jet.

 

[deerman2701]

Really? See I though it was the opposite. Cause the pilot is so big like 3 sizes up and the main is stock?

 

[Deuce]

Common fix with these bikes was to have the pilot at 48 (the factory pilot was too lean). The main is fine at 162 (stock main size). My bike is still at a 162 main even after doing motor work. I think my pilot is actually a 58 at the moment... its a little fat and I need to get it down to a 55. But my bike has a 13:1 piston and some other stuff, and I still get a little lean condition on decel (popping) even with a 58 pilot jet, and I do not have any air leaks.

Personally I'd put a new plug in it, and clean the carb. Start with a 48 pilot jet and keep the 162 main. Check your needle position and set it to stock.

To check the specs of the main jet, do a plug chop then pull the plug and read it. White is lean, black is rich... light tan/khaki is in the middle

To do the pilot you pretty much just have to ride it and listen/feel how it responds. If its popping a lot then its lean. If it pops a little, don't worry, read the plug again. The 426 always had a tendency to pop. If there is no popping but a low end hesitation / bog from closed to 1/4 throttle then your pilot circuit is too rich, and you'll have to go smaller on the pilot jet.

And then once you get them set away, you get to play with the needle. Easiest way I found to ballpark this, is put put the bike in neutral, and when its running, just maintain a throttle position to where its not wide open, but not idling. If its popping alot and running rough then you need to richen the needle because its lean. If it hesitates/bogs and has to catch up, once again its rich.

Once you get this all sorted out, the bike should be very snappy, with no hesitation (it actually scares my friends when I tell them to take it for a spin).


As for the heat... these bikes run hot. I had a leaf smolder on my head pipe, and my stainless head pipe (I have a jardine full exhaust) is nice and purple. They get hot... its the fact that these are high strung motors.

Finally, make sure your buddy is running premium in it... this will have an effect on everything because these bikes must have premium pump gas in them if they are stock.

Good luck

 

[deerman2701]

yea i mean it seems like its runing abnormally hot maybe its just cause im used to the warrior temp.

and also when you run it for a bit it seems to cut out and stall..

1 more thing is the bike runs a lot cooler with the choke on? why is that. it seems like a normal temp with the choke on. but if you run it with it off it gets real hot

 

[Deuce]

Which choke? The air (red) or fuel (black) choke? If its with the black choke its because the extra fuel is actually keeping the motor cooler. But like I said, these bikes get hot... and while you can let them idle, its not supposed to be for long... they need to be moving to get air through the radiators to cool it down.

 

[deerman2701]

Yup black choke the bike gets hot when running it and not when intun it with the choke on in the yard

 

[Deuce]

all your doing is cooling it down with fuel... fuel does cool a motor anyway, which is why running lean is bad. But it is dumping too much fuel with the choke on. You really need to read the plugs and check the tuning.

Like I said, these things run hot, last time I was out I got a leaf stuck between my head pipe and heat shield and it smoldered and smoked... I thought it was going to catch fire.

 

[Wolfsnout]

Change the tiny O ring on the pilot screw if the jet is not clogged. That will solve your problem. The header will glow a little red when sitting still. That is normal.