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Discussion Starter · #1 ·
Hi I have an 88’ 250R which I believe is mainly stock other than FMF exhaust and silencer. Has the stock carburetor which I just recently replaced all jets and cleaned up. I’m running 32:1 gas/oil ratio (93 octane). I also has V Force reed valve. I’m still having some bogging and throttle delay in lower gears. It doesn’t like to idle 😕 When I was rebuilding carburetor I noticed the needle clip was on the top groove. I changed it to the 3rd groove. When I got her all put back together it ran even worse. Bogging down more and didn’t want to stay running. I then moved needle clip back to top groove and it’s running much better but still bogging some in lower gears and there’s some throttle delay. Also still doesn’t want to idle much. Has 158 main jet and 45 slow. Do I need smaller or bigger jets?? Any other suggestions? Thanks so much! I’m in central Ohio with elevation around 900’.
 

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There’s a lot of jetting posts and tons of help if you have time to search “jetting” and read through them. I had jetting problems too and found a bunch of useful info. Your jetting sounds fine and needle position and main jet won’t effect idle so what’s your air screw and idle knob set at? Those 2 will change idle assuming your throttle cable is set adjusted right. Have you done a compression test and is your air filter clean?
 

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Discussion Starter · #3 ·
Thanks for the reply! I have not done a compression test. I will try that. Air filter is brand new. I did try running it without filter in case that was restricting airflow. It idled great for about 3 minutes (which is a first) then died and was a bitch to get started again. Choke was immediately killing it. Tried riding it without filter and it had same issues. The idle adjustment doesn’t seem to change anything. I’ve tried turning it all the way in and all the way out and various turns in between but it doesn’t seem to change anything. The air screw is currently 1 1/2 turns out. I’ve tried anywhere from 1 to 2 1/4 turns out. Is it maybe still running too rich?
 

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Discussion Starter · #4 ·
There’s a lot of jetting posts and tons of help if you have time to search “jetting” and read through them. I had jetting problems too and found a bunch of useful info. Your jetting sounds fine and needle position and main jet won’t effect idle so what’s your air screw and idle knob set at? Those 2 will change idle assuming your throttle cable is set adjusted right. Have you done a compression test and is your air filter clean?
There’s a lot of jetting posts and tons of help if you have time to search “jetting” and read through them. I had jetting problems too and found a bunch of useful info. Your jetting sounds fine and needle position and main jet won’t effect idle so what’s your air screw and idle knob set at? Those 2 will change idle assuming your throttle cable is set adjusted right. Have you done a compression test and is your air filter clean?

Thanks for the reply! I have not done a compression test. I will try that. Air filter is brand new. I did try running it without filter in case that was restricting airflow. It idled great for about 3 minutes (which is a first) then died and was a bitch to get started again. Choke was immediately killing it. Tried riding it without filter and it had same issues. The idle adjustment doesn’t seem to change anything. I’ve tried turning it all the way in and all the way out and various turns in between but it doesn’t seem to change anything. The air screw is currently 1 1/2 turns out. I’ve tried anywhere from 1 to 2 1/4 turns out. Is it maybe still running too rich?
 

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When you took the carb apart did you take the idle/choke out and clean it? Have you checked the reeds?
 

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Discussion Starter · #6 ·
When you took the carb apart did you take the idle/choke out and clean it? Have you checked the reeds?
I just changed the reeds to a new V Force reed valve
When you took the carb apart did you take the idle/choke out and clean it? Have you checked the reeds?
so I just changed the reed valve to new V Force reed Valve with 4 reeds. I did remove the choke/idle knob and cleaned it when I took apart the carburetor. I’m wondering if it’s still running too rich since the quad does not stay running when I activate the choke either? Like it’s already getting too much fuel. Would I have luck dropping main jet down to 155 instead of 158? Or even lower. If I do that do I need to stop slow jet down from 45?
 

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It shouldn't be running that bad with that jetting and it should still idle with a 45 pilot and the main jet has no effect on idle. You can try dropping pilot jet size and see if it'll idle. Did you just buy this quad and it ran like this or did it run good at one point?
 

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My nephew got an 88 last year that has pretty much the same mods as your's including the stock original carb. He wanted help tuning it because it was fouling plugs all the time. I told him the problem was trying to get that worn out 33 year old carb adjusted properly. He ordered a 38as, UPP intake & a motion pro 01-0604 throttle cable from ESR & brought it over yesterday & we put it together. The carb came with a 180 main, 48 pilot & DGH needle. We put the new parts on, fired it up & all I had to do was adjust the air screw. I still want to take it to the dunes to dial it in where it will be mostly ridden but that carb pretty much solved all his problems. The PJ carbs can be made to work well but its hard to tune one thats 32+ years old, the needle jets are non-replacable in the PJ so once there worn out they basically become throw away's.
 

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Something goofy is going on, I have almost the exact same setup on my quad and go back and forth between 45/48 pilot 155/158 main, stock needle right now on middle clip. I will be testing a DGH needle when I fix my tire. MN riding at 800-1000ft. I don't think jet size is your issue. Did you rebuild with OEM jets and not amazon mystery jets?
 

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Something goofy is going on, I have almost the exact same setup on my quad and go back and forth between 45/48 pilot 155/158 main, stock needle right now on middle clip. I will be testing a DGH needle when I fix my tire. MN riding at 800-1000ft. I don't think jet size is your issue. Did you rebuild with OEM jets and not amazon mystery jets?
Ok hold on now too lol I have a stock 250r but only modifications is an FMF fatty with pro circuit 304 and and ESR airbox eliminator kit. My jetting is set at 48 pilot with a 160 main. Air screw is out at 3 and like 1/4 turn, yes I know thats out alot buttt hear me out. The other day I reset the airscrew starting at 2 turns out and it didnt like it. Ended up at the same spot 3 and 1/4 turns out. The only thing scaring me right now now is having the airscrew that much out and blowing the bike up. Any possibility of it blowing up with the air screw that out? Bike has 20 hours that I put on it since I bought it and hasnt blown up or anything, but I lowkey getting scared it might. The carb right now I have is a PJ. My only issue is it bogged out on my while giving it a quick snap of the throttle from idle but maybe it was cold and not fully warmed up. Compression from kicking the bike over feels great and the same as before. What do yall think might blow up with the airscrew that out and why would it bog with a quick blimp of the throttle?
 

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Ok hold on now too lol I have a stock 250r but only modifications is an FMF fatty with pro circuit 304 and and ESR airbox eliminator kit. My jetting is set at 48 pilot with a 160 main. Air screw is out at 3 and like 1/4 turn, yes I know thats out alot buttt hear me out. The other day I reset the airscrew starting at 2 turns out and it didnt like it. Ended up at the same spot 3 and 1/4 turns out. The only thing scaring me right now now is having the airscrew that much out and blowing the bike up. Any possibility of it blowing up with the air screw that out? Bike has 20 hours that I put on it since I bought it and hasnt blown up or anything, but I lowkey getting scared it might. The carb right now I have is a PJ. My only issue is it bogged out on my while giving it a quick snap of the throttle from idle but maybe it was cold and not fully warmed up. Compression from kicking the bike over feels great and the same as before. What do yall think might blow up with the airscrew that out and why would it bog with a quick blimp of the throttle?
Nevermind I found this on a "jetting database" on here

Many people say this:
air screw - idle to 1/16 throttle
pilot - 1/16 to 1/4 throttle
needle - 1/4 to 3/4 throttle
main - 3/4 to WOT

BUT the range of the jets actually overlap.

Air screw - off idle to about 1/4 throttle
The air screw meters air to the pilot jet

Im just overthinking it lol air screw is for only for 0 to 1/4 throttle. Still a noob to the two stroke, this TRX is my first bike I have ever owned. Im a lucky guy lol Then after all this overthinking my jetting seems right except my air screw still being so far out.
 

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Nevermind I found this on a "jetting database" on here

Many people say this:
air screw - idle to 1/16 throttle
pilot - 1/16 to 1/4 throttle
needle - 1/4 to 3/4 throttle
main - 3/4 to WOT

BUT the range of the jets actually overlap.

Air screw - off idle to about 1/4 throttle
The air screw meters air to the pilot jet

Im just overthinking it lol air screw is for only for 0 to 1/4 throttle. Still a noob to the two stroke, this TRX is my first bike I have ever owned. Im a lucky guy lol Then after all this overthinking my jetting seems right except my air screw still being so far out.
I think your plenty safe. Look at your plug, you might be able to lean it out. OEM bone stock jet sizes are 45/152. Id stay away from going below that. Every quad is different though, and I'm no professional.
 

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I think your plenty safe. Look at your plug, you might be able to lean it out. OEM bone stock jet sizes are 45/152. Id stay away from going below that. Every quad is different though, and I'm no professional.
Same im a complete noob to the 2 stroke, you know I might try a 45 pilot like you and see if I can lean her out just a hair. Where do you get genuine PJ jets at? Also im running 40:1 on her with Amsoil Dominator.
 

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Discussion Starter · #14 ·
My nephew got an 88 last year that has pretty much the same mods as your's including the stock original carb. He wanted help tuning it because it was fouling plugs all the time. I told him the problem was trying to get that worn out 33 year old carb adjusted properly. He ordered a 38as, UPP intake & a motion pro 01-0604 throttle cable from ESR & brought it over yesterday & we put it together. The carb came with a 180 main, 48 pilot & DGH needle. We put the new parts on, fired it up & all I had to do was adjust the air screw. I still want to take it to the dunes to dial it in where it will be mostly ridden but that carb pretty much solved all his problems. The PJ carbs can be made to work well but its hard to tune one thats 32+ years old, the needle jets are non-replacable in the PJ so once there worn out they basically become throw away's.
I’m gonna try that I think. I just screwed around with it for past 2 hours. Tried 160 main, 162, and 165. Solved my top end problems at 165 main but low gear problems (1st and 2nd) still existed. Tried bigger slow jet at 50, no go. Tried lower at 42, a touch better maybe but still a no go. I’m gonna order same thing you tried and hope it solves my problems. She screams at top end now but such a pain in the but with the sputtering and slow acceleration with lower gears.
 
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