revs high

[Rideblue4ever]

i just rebuilt my whole engine and now that i have it running i warmed it up and took it for a slow spin and it revs REALLY high when i pull the clutch in and when i let it out it doesnt..i dont wanna blow my engine the first day i got it running so what could it be please help?

 

[Moparman1539]

lower the idle speed

 

[rosscopeeko]

If it's colder outside now than when you normally ride your jetting may be a little lean and raise your idle up and make it surge and vary.

 

[Rideblue4ever]

what should i do to make it richer?

 

[Trashrider]

It sounds like an air leak, get that sealed up. It will melt your piston! Check your carb clamps and main seals. I don't want to alarm you but it could be costly if you choose to ignore this. Perform a leak-down test.

Mark

 

[Rideblue4ever]

thanks...i checked my carb clamps and the one that holds the carb to the reed valve boot was REALLY loose so hoppefully that is the problem..i would really hate to melt my piston seeing that i just put all that money in to it.. thanks again tho

 

[Rideblue4ever]

well i started up my bike today its cold and rainy out but it still revs high and im pretty sure the air leaks are takin care of. how do i do a leak down test or w/e...and could it really be the jetting and what should i change in the jetting becuase the carb is all stock

 

[griffbones]

Make sure the throttle cable isn't binding up or mis-adjusted, this could prevent the slide from returning all of the way back down.

 

[Rideblue4ever]

i didnt even think of that..becuase i removed the throttle cable and electronics when i was rebuilding the engine so i may have mis routed the throttle cable..thanks so much i hope thats the issue

 

[Rideblue4ever]

yea its not the throttle cable and it cant be a air leak..ive had the engine apart 2 times and made sure every nut and bolt was tight as possible and that the gaskets were in palce..so what should i do to the jetting. it has got to be a lean condition

 

[griffbones]

This is a little bit strange in the fact that most times that I have done a new top end, the jetting may seem slightly richer afterwards.
1. I would give the carb a really good cleaning to make sure nothing is plugging up the pilot circuit and making it lean at idle. I can't hardly believe that the jetting could have changed so much that it would be reving that high, not if the jetting was correct before the rebuild.
2. Have you tried spraying brake cleaner behind the mag rotor while the engine is running? If it changes the speed of the engine then the left crank seal is sucking air. Just be real careful doing this one - spining parts can bite you!
3. To be honest it really sounds like an air leak somewhere or a carb slide sticking or hanging up. With the bike shut off, if you roll the throttle open and then let it go, can you hear the slide seating back down in the carb? Make sure that slide isn't hanging up!

 

[Rideblue4ever]

im gona try that brake cleaner idea..and im gona try it around where u split the cases at hopefully il find it cuz i really wanna ride but dont wanna burn up a piston dion it

 

[Rideblue4ever]

Yz250

i have a yz250 and my bike revs high when its idleing..people have told me its a air leak but i took starting fluid and sprayed it on the left side crank seal and theres no leak and all over the cases where i split them..im beggining to think its just jetting..its a 2000 and there stock jets..where should i start

 

[burgunder]

First, turn out the idle screw. If that doesn't lower the rpms at all, turn the air screw in a 1/4 at a time. This will richen the first 1/8 of your throttle effectively lowering your idle. If you can turn the air screw all the way in and it does not lower the rpm's, you need a smaller air screw. Once you have the idle figured out, set the air screw for the best throttle responce. Read the jetting posts.

 

[Rideblue4ever]

alright il do that...why would it change so much tho i only replaced the bottom and top end didnt mess with the carb none?

 

[Trashrider]

At this point I would verify what jetting is supposed to be from the factory. Look in the manual and compare that to what is actually in the carb. Go back to factory specs and work from there. It is possible that a previous owner jetted the bike so far off that a fresh top end won't work with it.

Mark

 

[Rideblue4ever]

can a RIGHT side crank seal cause this because i didnt not change that one out? i no u guys are prob about to tell me to just take it to the shop but thats not a option because i dont feel like spending hundreds of dollars for labor...but i think i should order new seals and gaskets and take everything apart and go over it again and then jetting

 

[griffbones]

Are you 100% sure that the slide is returning all of the way back down. The idle speed screw isn't cranked in too far or some thing weird like that? The needle is properly installed in the slide and not out of place? I'm not trying to insult your intelligence with these questions, but I have run into some strange things over the years.
I can't picture this just being a jetting problem if it ran ok before the rebuild. A weak top end (low Compression) acts like lean jetting, and normally after a top end they will actually run slightly richer not leaner.
BTW- if the right side seal was leaking it should be sucking trans oil and smoking really bad. As mentioned above, check to see what jets are in the carb now, maybe a previous owner did some wacky jetting.

 

[Rideblue4ever]

it ran perfect before it seized...the only reason it seized was cuz i had it pinned in 5th gear racing a Cr125 on the road and i was runnning 89 cent oil the cheap stuff..but i guess il break out the manual and go throguh the whole carb and put everythign to stock..and it doesnt burn tranny fluid so it cant be that seal and ive sprayed starting fluid all over the enegine and in the stator housing and nothign changes..so il do that do the carb...it is colder out side then when i last rode it

 

[griffbones]

Have you checked the float level by chance? If the float was sticking and not allowing the bowl to fill up, it could sure make the engine really lean. Just another crazy thought I had to throw out to ya.
Here is another one for you to check; make sure the slide isn't worn and hanging up in the bore of the carb. I know these are remote chances but worth checking out.

 

[Rideblue4ever]

when i had the carb off..is the slide supposed to be open a little bit or closed all the way? becuase it is open a littel

 

[griffbones]

The slide should be down all of the way on the sides, but there will be a cresent shaped cut-away so it will have a very slight opening opening in the middle. If that makes since to you.

 

[Rideblue4ever]

yea that makes sense to me...i wanna ride so bad lol..i wish i wouldve had ashop do the bottom and top end it wouldve been easier in the long run or atleast the bottom end

 

[Rideblue4ever]

i have found the problem...it was indeed the left side crank seal..i did install a new one but i guess i damaged it puttin in in....i did the starter fluid test and it didnt rev up so i didnt htink that was the prob...i found out it was the problem when i was going to take the engine out again and i turned the flywheel/stator and i heard air pushin out of it...but i thank all you guys that have helped me out..

 

[griffbones]

Congrats glad you found it! :cool: :nod: :) :cool:
Sometimes it is hard to spray right on the seal since you can't see it and the rotor is spinning, but this test has worked for me before.