main jet inquiry - help needed By godfeast (Read 2,043 times)

[godfeast]

Alley, dont have anything between the 120 and the 125 range - are you saying I should pick up a 124?

I played with it until I lost all daylight - bike no longer backfires but bogging is bad at top end and almost gone on low to mid now.

Fix one, break another - damn.

I have one last trick in that I have an old stock muffler laying around somewhere and may toss that on instead of the free flow one and maybe I can get that 120 or 114 to do the trick again afterwards.

If that doesnt work, I'm not really sure where to go from here.

[alleyoop]

HOW DID YOU GET RID OF THE BACKFIREING?
The usual cause of backfireing on decleration is a AIR LEAK and many times it is leaking by the FLANGE where it connects to the motor. Or leaking really bad by the Intake Manifold and or Air Filter side.

Sorry godfeast, I read your post wrong and I thought you said you had a 124, But you said it was running pretty good with the 120 except for a little bit of bog at around 35mph or so and once past that it would run good. So with the 120 it runs good but just a little lean on the top end but to much in the middle, which would make sense. So most likely a Jet between 120 and 125 would be good for the top end but you would need to drop the needle for the mid-range.

What is puzzling to me is that it is taking a 120 main jet just for a free flow exhaust and a free flow filter. Normally a 24mm carb comes with a #35 pilot and a main jet anywhere from 103-107 and if you put on a free flow filter you go 2 up on the main jet if you then add a free flow exhaust you again go 2 up on the main jet. So normally a 115 would do just find. Let me ask this Have you OILED THE UNI FILTER? Because if you haven't that is throwing it off the uni with no oil sucks in a lot of air which in turn would require a lot more fuel.
Alleyoop

[godfeast]

Well, the 120 was chugging when I let off the throttle, but you said that plug looked lean, so i went back to the 125.

The 125 though, almost immediately cause backfiring on deceleration and some chugging still.

Ive spent all afternoon and into the evening taking the carb apart and tweaking the needle and the float to try to get good settings, with no real good result so far.

The backfire seems to be gone, but then again with the bogging towards top, I got frustrated and took it right home only a few minutes into the test ride - could still be there I suppose.

The uni is oiled - never ran it unoiled. Ill oil it again tomorrow just to be certain its coated.

Im not certain if I should get a new carb to make sure im not dealing with anything that might be broken with this one , or if I should go back to the stock muffler, or both.

I know in the past that the muffler to exhaust port bolts have come loose and caused lean conditions leading to two of my top end failures, so I made a ride on the outside of both bolts a while back and tie piano wire between the two bolts so they wont back off - cant figure another way around that issue.

Ill take thee wire off and check again tomorrow to see if they backed out - could be an issue too; sometimes I wonder about the design on these gy6's...

[alleyoop]

Might not be a bad idea getting a new carb, since you said that one had dirt and or sand in it which could be blocking air passages. I would try putting the old muffler on the one on there can not be creating enough backpressure giving you grief.
Alleyoop

[godfeast]

Seems my post didnt take.

Put old muffler back on - sounds louder than it did way back when (so quiet it sounded like a whisper) - no ideas on that except that maybe the gasket or exhaust studs are loosening again. meh

Rode and it had power, sounded fine except at wot every 6-8 sec or so theres a dead spot for 1 sec and it keeps repeating.

Any ideas on this?

Out of time for today, but still need to get it right.

[alleyoop]

Great, so it appears it was your muffler that was causeing the greif.
What kind of dead spot, was the motor making any kind of sounds. Burp sound, POP sound BOG sound etc.
Alleyoop

[godfeast]

nope. It just lost power like i had let off the throttle for a brief instant then right back to running fine - no weird sounds or anything else.

I'm still not sure the muffler sounds right - its a bit odd. Ill try to listen harder tomorrow and describe it better.

Do you think running rich would cause such a short loss of power at wot?

[godfeast]

I decided to go with my gut feeling that keeping a 125 in an engine with A now more restrictive muffler and a highly overoiled uni filter (lol) wasnt a good idea.

I went back down to my 114 and it seemed to runs pretty decently - still a bit of a backfire on decelleration (not much but there), so I adjusted the needle as rich as possible and that still hasnt really solved it.

I took it for a short wot spin and it immediately started to backfire loudly and died a few times. Took it home and putting a 120 back in

More confused than ever.

[godfeast]

OK, playing with it a bit more.

1. stock muffler now on and tight without leaks

2. found a slightly smaller idle jet and put it on (unknown size, but a hair smaller than what was in it - pulled from another junk carb).

3. Needle put at half way point

4. Float adjusted to slightly lean - not by much, maybe a half mm from where it should be.

5. 120 left in as main jet


Seems to be running fine - no backfire, muffler a bit loud than I recalled still, but no obvious issues.

No oil spewing and top end is now out of break in.







verdict?

[alleyoop]

Looking Good But I would get the 122 main jet because of the way you ride at WOT most of the time. I would get it a little richer on the top end.
my .02
Alleyoop

[godfeast]

I thought it looked a little on the rich side already (am I wrong again alley?) - thats a chop after wot riding for 3 minutes - wouldn't that screw up my idle again do you think, or could I compensate with the needle since Im already at the half way point (only two slots to move up)?

Just want to make sure before I place an order tomorrow.
placed an order for a 122.5 (no 122 it seems).