Main Jet Confusion??

[MPNX2]

Ok I have gotten my X running pretty good now I just have some jetting issues. I am running really rich and according to the article I read it says to start at the top of the circuit and work down. So I am currently running a 138 main jet in my Keihin PD28A carb. I went and got the next jet smaller which is a 135. I put in the 135 and the motor just refuses to start. To me this just doesnt make any sense the main jet shouldnt effect this part of the circuit. So why is this happening???

[Tri-Z Pilot]

Hmm, youre right, maybe your slide is open just a little, and your pilot is lean, so it is getting it's little bit of starting oomph from the main jet.

[MPNX2]

OK I just got done putting the 138 jet back in and it starts on the second kick. So what do I do from here?? Maybe I should just leave the 138 in and adjust the clip or the pilot screw??? I dont know??..

[Tri-Z Pilot]

Try this, unhook your throttle cable, make sure the idle adjustment screw is backed out, richen up your idle mixture screw, then try starting it with your smaller mainjet.

[MPNX2]

Try this, unhook your throttle cable, make sure the idle adjustment screw is backed out, richen up your idle mixture screw, then try starting it with your smaller mainjet.

Ummm!! No that didnt help either... What a pain!!!

[Tri-Z Pilot]

Hmmm, that's really strange, maybe your trike is cursed,lol!

[MPNX2]

Now I put the 138 back in and it still isnt starting!!!!!

[MPNX2]

I pulled the spark plug and it was wet. Can a motor get too much fuel and cause it not to start??? This is rediculious.............. :!: :!: :!:

[Tri-Z Pilot]

Yep, try cleaning the plug, or install a new one, or try this, hold the throttle wide open, then try starting it, this works if your engine is flooded.

[MPNX2]

I have given up for the night on it. I live to fight another day.....

[MPNX2]

Yep, try cleaning the plug, or install a new one, or try this, hold the throttle wide open, then try starting it, this works if your engine is flooded.


It still didnt seem like it wanted to start. This really doesnt make any sense...

[86waterpumper]

you may have washed out the cylinder. May have to put some oil in the spark plug hole and work the kicker by hand to build the compression back up.

[Tri-Z Pilot]

Washed out the cylinder? What do you mean, I have never heard this term.

[Tri-Z Pilot]

I just saw your other post, about a black sooty plug, and you said that you just rebuilt your motor, this may be your problem. Until your motor breaks in, it may dog a little, and foul plugs, because everything is not seated yet, and you may be burning some oil,(this is normal for engine break in).

[86waterpumper]

The term "washing out a cylinder" refers to what happens when a bike is jetted rich, and is constanty kicked or cranked etc, and floods until raw gas washes all the oil off the piston rings, and there is no compression. It can happen on cars as well, or any other motor. My 200x did this, soon after it was rebuilt. When one does it, you can pretty much row the kickstarter without any effort at all. To get the rings to seal back, sometimes it's necessary to get some oil back on the rings.

[TimSr]

I obviously was not there to observe, but something else has to be going on. Some other change had to occur during the change from a 138 to a 135 main jet, because I do not believe it it possible for that jet change to be the cause of it not starting unless the hole in the jet is plugged.

I had a problem with the Z a where for some reason fuel was flowing into the cylinder when it sat with the gas one. I could come out the next day, and it would feel like no compression, just as Waterpumper was taking about, and Id have to take the pipe off, pour out the gas, take the plug out, and let it set open for a day to dry out. A little fire in the plug hole speeds it up, but it can also be very dangerous!

Its hard to guess what is causing it to not start, and I cant tell you if the jet change was right, but if it starts with a 138, it should start with a 135.

[jason200x]

i had problems with mine running to rich and still cant find the problem sometimes it feels liek no compression but then it comes right back? it will pope really bad at higher rpms and wont go to full speed, it doesnt iddle either, and if im rideing it feels like when you let off the gas it jus stops giveing spark, when it get warm i have to turn the gas off turn the choke all the way on then kick it 6 or so times to get it to start and right when i kick i have to give it gas and keep taping the throtel to keep it running or itll die, im getting tired of it but water pumper told me some problems it could be and if its not fixed by this week its going to the shop and im just gunna tell them i want it to start 1st or 2nd kick and first kick when its warm i want it to iddle good and not have to turn the gas off to start it back up!!!! lol or else

[MPNX2]

Ok so what do I do now? The motor is not wanting to start with either jet in it so what should I do to at least get it started again??

[86waterpumper]

In another post you said mpnx2 that you had a xr carb to put on the bike. Your keihin pd28a is this a 26 or a 28??? At any rate, a 28mm carb or a 138 main is pretty hardcore for a 200x, unless it's beefed pretty good. Most people that run 28's have 12:1, some porting, and a pretty radical cam. a 26 does sound about right for your mods. I agree with Tim though, the main will not hinder it cranking, the main has very little if any effect on idling and cranking, I'd think that would have to do more with your airscrew settings, and pilot circuit, needle etc. I think both your bike and jason's are simply running stupid rich, like my old x did so long. I tinkered with mine forever, and had black sooty plugs, cutting out on the top end, hard cranking etc. I tried taking the airlid off, leaning the clip out all the way, 108 instead of a 110 jet, everything I could think of. I got it rideable, but it wasn't right. Finally cat took it apart and found out that a tiny air jet was plugged up with dirt or something. I had rebuilt the carb and cleaned it, but I'd used low pressure spray air out of a can to blow it out, instead of a high powered compressor, so it just wasn't powerful enough blast to get all the grit out. Once the issue was fixed, had to go up about three sizes on the main, put the needle on next to the richest setting, etc, which is what you'd expect to have to do.

[MPNX2]

The carb is a 26mm. So I guess I should take the carb off the bike and look at the pilot jet which is located inside the bowl and see if it needs to be cleaned. Do you have any idea at what I should set the air, and idle screws at just to get it in the ballpark??? Maybe 1 1/2 turns on each???

[MPNX2]

Well I took the carb out of the bike and remove the bowl and all the jets and blew them out with air. I also checked each one to make sure I could see light through all the holes in each one too. I cleaned it again with some carb cleaner and put it back in the bike. Still it is refusing to start with either jet in or with the choke on or off.

[jason200x]

does it have spark? try takeing the plug out and makeing shure its still good and make shure the tops not bent, iv had the same problem but mine was just that the plug bent at the top. check your plug and see if its wet, if it still wont strt pull the plug and spray a lil carb cleaner or soem engine fire up n the cylinder, make shure all the boots are tight, try a new plug,