90 hit the gas and it boggs

[procraft7399]

I have a 90 drr when you are stoped and hit the gas wfo it sometimes boggs and you have to feather it to get it going like the choke is on(but it's not) then sometimes it just screams off, also it seems to be missing while he is on the gas I thought I heard a backfire. I cleaned air filter changed fuel filter check plug it was good, but still has trouble. Any ideas? One more thing you have to give it a little gas to get it started (cold).

[nastynotchback1]

Sounds like your jetting is off.I have had this problem when the plug was bad.Looked good but it was bad.does it do it on the stand also?

[procraft7399]

I haven't changed jetting or put it on the stand. Will try the stand.

[chris p.]

pull carb off and clean,clean clean.make sure main and pilot jets are spotless and make sure small holes in pilot are clear.CAREFULLY use compressed air.jets like to go flying.LOL. :D

[procraft7399]

I just tried to check the compression, I kicked it 1x and it only had just a little over 60 psi if I did it correct? How do you check the compression?

[EthansDad]

With the gauge in, hold throttle wide open and kick it 10x times or so

[nastynotchback1]

i don't think it would even run with only 60psi.I would try that again.

[procraft7399]

Ok, it has 2 b dirt in the carb, I check the compression kicked 10x with wfo and 160 psi. will post results.

Thank you

[dewutfan]

it still might not be dirt in carb .. yes clean it .. but it might need to be rejetted .. sounds like ploit jet might be off...

[procraft7399]

Ok, cleaned and it wasn't dirty at all. So now the jets? What it does is when you are just sitting at idle and hit the gas open sometimes it boggs down then goes sometimes it doesnt, seems to run at high speed I thought I heard it backfire one time. About the jets I took out 2 one was 2 pieces and the other was just single piece that came out with screw driver other a socket. Which one do I change and do I go bigger or smaller? Thank you for your help.

[dewutfan]

one with the socket is called your main jet the one with screw driver slot is called the pliot jet... they should have numbers on them ... on the main it should be numbers like 105 to 150 and the pliot could be from 38 to 50.. you need to see whats in there so you know which way to go... mine is set with 48 pliot and 135 main.. but every one is different..it sounds to me you need to start by putting a bigger pliot jet in .. go up by 2 then check it go up 2 more and check it again untill it hits the sweet spot then stop... because if you saying it runs great on top end sounds like main jet is good... and make sure your air screw is adjuted out 1 to 2 turn out any less or more you need to go another route... hope this helps...

[Logan #34's Dad]

Originally posted by procraft7399
Ok, cleaned and it wasn't dirty at all. So now the jets? What it does is when you are just sitting at idle and hit the gas open sometimes it boggs down then goes sometimes it doesnt, seems to run at high speed I thought I heard it backfire one time. About the jets I took out 2 one was 2 pieces and the other was just single piece that came out with screw driver other a socket. Which one do I change and do I go bigger or smaller? Thank you for your help.

Okay, the one that is two piece is your main jet. Its not supposed to come out that way to change the main though. separate the two by using a 10mm wrench and a 6mm socket, reinsert (thread) that longer part back up in the carb - be careful of the needle which goes inside that long part. Tighten that half down pretty snug with a 10mm socket up in the carb. From there you'll change the main using a 6mm socket.
My experiance is a 42 pilot and a 128 - 135 main is about right using VP C12. Air screw 1 1/2 turn out.

[procraft7399]

well it appears as though we have fixed it but it was only garage and backyard testing. It had a short 55 piolt the only jets the parts shop had was a long so I put in the 60 long it fit fine and appears to run great at this point. Will I have a problem with the 60 long? The carb is a Keihin PE not sure what size. Thanks to everyone who help me out. Thank you.

[Logan #34's Dad]

I don't quite understand the terms "short" and "long" when you discribe the pilot jet. The pilot jet is the jet that you have to take the carb bowl off to get to. It requires a little screw driver to take it out and in. For a PE it sould be about an inch long with little holes above the threads.
A 60 sounds way too big imo. I'm in Ohio and run a 42/45.

[mmsoup]

We run both short and long Pilots with little to no issues between the two. I have heard of pickup issues with the short pilots but never experienced any.
Rocky is right, that is a huge pilot, we run Haggerty intakes with 28mm Keihin D Slides and the largest pilot we have run is a 50. The TT guys like the big pilots for fuel pickup out of corners but ours really run snappier around 45-48
Too many other variables unknown in your post with respect to intake, carb size and snorkel if any
First time I saw your post I thought to myself "Lean Bog" and the bumping at the top sounds like a lean top end, the fact that you are putting that much fuel to it to make it run, kind of supports that thought, is this a new machine or was it acquired used? Have you looked at your plug? What color was it?
Has the motor been checked for air leaks?

Just curious

[procraft7399]

mmsoup:

used machine, plug brown (not black, not oily), not checked for air leaks, no snorkel, keihin carb PE not sure what size, how do you tell? How can I tell it the motor has an air leak? will it make a distinct sound? I will have the boy run it tomorrow.

[mmsoup]

Plug color sounds good but with all that fuel it should be real dark. I haven't run PE carbs in a while but I seem to recall thay used slightly higher jetting just not that high. At any rate the size is not indicated on the carb (I checked the two I have)
If you know someone who has a leak down kit, it wouldn't hurt to know if the motor is tight or not. Should hold 6 lbs psi for at least 5 minutes with zero loss. (Exhaust blocked off and tester plugged into intake)

How does it idle? is the idle stable or does it run up and down? Can you easily adjust the idle with the idle screw? Where is the air screw set?

[procraft7399]

Nothing good to report ran about 20min, still bogged some, half to 3/4 throtle sounded like it was missing, stoped to get a drink and when he hit the gas it just bogged out and wouldnt rev up at all pulled it back into the garage. Pulled plug tip still brown but I think there was more oil on the treads this time? Cleaned air filter, checked fuel filter for dirt from tank (no) drained some gas from tank 40:1 mixture no debris. It has a koso intake system. I haven't done any wireing or changed anything else. No backfire on or off gas, air screw 1 1/2 turns out. Because of the heat should I go smaller on the jet's, I went bigger? Thank you

[dewutfan]

yes you need to go down om that pliot jet its to big... try a 42 or 46 ...

[mmsoup]

Try a 45 pilot and leave the air screw where it is. Leave the main where it is and see what happens. slowly step down the main from there.
Bogs are normally lean so I am worried about leaks still. As you take fuel away heat will happen quickly if it's leaking so be cautious and check plug frequently
May just be super fat but never hurts to be careful

[Logan #34's Dad]

Also you need to check your needle position. Have the quad up on a stand warm it up, hold the throttle at half way. The engine should stay the same or continue to rev a little. If it does not perform right, take the top of the carb off and adjust the clip on the needle until its right.

[procraft7399]

Well went down to 45 pilot and it is runing much better not great but better. However that wont matter b/c he clipped a tree and pushed the right front 2inches back and the frame is broken. So at this point the engine is the least of the problem. Thank you for all your help.

[mmsoup]

Welcome to our little slice of paradise!

Keep at the jetting when you get a new set of arms

[wrhracing]

If He has a Kehin round slide the 20mm comes with a 58 pilot. different style carbs see different signals from the engine hence different jetting for different carbs.