Stock YX160 Rebuilt, Hard starting, rough idle.....stumped.

[DHXrider]

Hi guys,

Just throwing this out on a few forums trying to get feedback. I just rebuilt a YX160 stock engine, new valves, piston rings etc. + transmission. Followed steps by book. Have done a few rebuilds so know what I'm doing. Made sure valves sealed etc. Good compression, all the main criteria are accounted for.

I installed the engine a few days ago using the same carburator that worked with it last year(motor ran fine last year, just did a preventative rebuild over winter). Now the bike literally does not get gas into the chamber no matter how many times I kick. ----->>logic says carb.------>swapped the carb for one that I know works on another YX160 and got the bike started and running ok.

Here's the weird part, since I narrowed it down to a carb issue, I put the original carb on and tried adjusting it, air mix screw, idle, choke on off etc. and it worked.....!! great. All is good....

Ok, so go to start bike today with the orgininal carb that I thought I managed to get working and it idles rough, some cutting and surging in 0-1/4 throttle, rough idle, will stall if idle is too slow, seems to stall right after I open it up in third or fourth. But at times it will run super smooth like there's no issue. I'm hesitant to play with jetting because it's using the same jetting AND settings as the carb that worked on it a day ago, the one I used for a test swap. I usually try to use as much logic in troubleshooting issues but now I'm stumped. Thinking flaky carb, dirt logged in it ? It gives very flaky performance, now I can't even start it again after many kicks, I took the plug out and not gas getting to chamber........

also, swapped CDI, no effect.

cleaning carb tonight........we'll see.....it's a new style molkt carb with large bowl. keep in mind it worked great all last season on the same motor...

thoughts, comments...

J
www.dirtforcemotorcycles.com

 

[SIKKO_X2]

Could be a blocked jet in the carb?

 

[my67xr]

yeah as above,
it may have something stuck in the needle and seat, not letting fuel into the carby ?
opening the fuel bowl drain screw will confirm this.

otherwise the pilot jet has something blocked, either in the jet, or the little gallerys off the side after the jet ?
or possibly in the gallerys where the jet screws into.
pull the carby off, and down into pieces
spray some carby cleaner through the air filter side of the carby and make sure it comes out inside the jet ports etc.
have you chcecked where the pilot jet screws into, there is a small port, which continues into the carbys' bore, check that is it see though, with the jet removed.

 

[GooseMan]

Sounds like you should give the carb a good clean out with compressed air and set your mixture screw to 1.5 turns out and go from there.

Is that your bike in the link? I like it alot.

 

[DHXrider]

yeah, I'm narrowing it down to pilot jet just like your guys are saying. The float bowl fills up because it spills over when I'm working on it. The seat might be flaky though, I've had it happen before, makes things go all screwy so we'll see. I have the main jet out, left the pilot in while I soak whole carb overnight. I'll inspect tomorrow and post.

 

[my67xr]

very nice bike, i want the frame/swinger !

 

[DHXrider]

Yeah, they are insane!

PM your e-mail address, I can send you our order form....

 

[my67xr]

a vacuum leak could cause you idle problems too.

before you take the carby off, start it and spray some wd40/degreaser etc onto all the joins, carby/fuel bowl, carby to spacer/insulator, spacer/insulator to manifold, manifold to head etc
if the idle changes in any way, then there is your vacuum leak.


when you have the carby apart, check the fuel bowl to carby base to see if it hasn't warped.
then check the manifold side of the carby, the mounting face, and both ends on the intake manifold too just to be sure.

 

[my67xr]

Yeah, they are insane!
PM your e-mail address, I can send you our order form....

thanks for the offer, but a complete bike costing $5000CAD plus postage is a bit out of my price range, lol

cheers, craig

 

[DHXrider]

No worries Craig. Seriously, I understand. Just so you know, the frame kit option comes in @ 2200$, it gives guys a chance to save money and throw in their own spare parts they might have lying around. Believe me, keeping costs down is tough, I'd like to give them away but when you add everything up, the prices are what they are. Figure the YX160 engine with all accesories and shipping pushes 1000$ alone. It just adds up

l8tr
Jon-

 

[Hussey]

For another opinion, definately sounds carby related. Double check the plug also.

 

[DHXrider]

Yeah, carb related for sure...from past experience, usually rough idle means air leak. I've never tried the WD40 trick though. I'll try it out if I can start it. No question I'll get it going, just a matter of troubleshooting it. Carb is still soaking. Will post up results soon.

J

 

[zwebx]

Yeah, carb related for sure...from past experience, usually rough idle means air leak. I've never tried the WD40 trick though. I'll try it out if I can start it. No question I'll get it going, just a matter of troubleshooting it. Carb is still soaking. Will post up results soon.

J

yeah, i had one leak so big that it could start with full choke and only idle... the fix was two gaskets between the carb and the plastic spacer because the carby was warped

 

[DHXrider]

hey guys,

Just thought I'd do an update. So I soaked the carb for two nights, got the air compressor and blew air through every passage, there were a few that definitely seemed like the air built up and then blew out meaning they were tight or blocked, one that comes to mind is the tiny pipe that feeds into the choke. I probably should have done this to start with, especially since the carb had been sitting over winter, prob gas varnish build up. Anyway, now the bike starts and runs great. So it was definitely a carb issue as the symptoms suggested. Hope this helps someone in the future.

 

[my67xr]

it's good to hear you got it running again.