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Post by rcq92130 on Sept 14, 2014 18:27:35 GMT -5
OK, will screw out the mixture screw a bit.
Idle is at about 1800 RPM (see video), so I guess it's a mixture problem.
Yes, it's a "Red" uni - I removed the "red" dust sleeve so it would be easier to put the latex glove on.
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Post by rcq92130 on Sept 14, 2014 18:11:38 GMT -5
Thanks, Alley. Had no ideas that was an unusual Uni.
I'll first open the diaphragm cap and see if the needle valve is adjustable (that way don't have to take the carb out, which is a pain with this carb). Maybe, if it's adjustable, I can raise the needle enough.
If not, I'll try a 125 main jet.
Thanks again.
>>"That is a pumper carb which does not have an ACV valve to help when the throttle is suddenly closed and coming down to idle to feed it some fuel so it doesn't run lean on de-cel.
so, the popping is "normal" with a pumper carb?
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Post by rcq92130 on Sept 14, 2014 17:55:13 GMT -5
Yeah, I have a BMS. Looks pretty similar to yours (incl the stainless floor boards)!
So --- you are going to raise the carb up so the pipe to the air filter goes OVER the cross brace, huh?
That means you will sacrifice your under-seat cargo box ... right?
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Post by rcq92130 on Sept 14, 2014 17:29:47 GMT -5
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Post by rcq92130 on Sept 14, 2014 16:54:17 GMT -5
This is a continuation of the earlier "bucking/stuttering" thread that got pretty unwieldy. Recap: New 60mm BBK ran great for 20 miles, then a slight misfire happened and within 1 mile the scooter barely ran well enough to limp home (150cc GY6). At first everyone thought it was too lean, but I was unable to solve the problem with jet swaps. Then the idea was electrical; everything except the coil was swapped with no effect. So I ordered a 30mm carb (wanted a larger one than the 24mm stock one anyway) and a "performance" coil. Coil is still in transit; carb is installed. Using a 38 pilot and 120 main Stuttering better but still pretty bad: Good news: turning rhe idle mixture screw DOES change the RPM (unlike the stock carb). Engine at WOT races from idle (1800) to about 5,000 without a hitch. Was able to set idle mixture to, I think, best position using Alley's tuning PDF. Bad news: carb is very tough fit - pumper body prevents level install because it hits against the crankcase forging of the engine mount (see first photo - off by maybe 5 degrees). Though idle is very good, and RPM increase at WOT is smooth up till about 6K RPM, it then completely bogs down and won't go to a higher speed unless I turn the throttle back to about 2/3 WOT (RPMs then race upwards ... I stop at 7K since I have new piston rings). Some popping or backfiring on decel. Tried decreasing the Uni flow by putting a vinyl glove around about 1/2 of the filter (see photo 2) and this helped --- WOT now goes up to about 6,000 before bogging, and if I keep the throttle at WOT the engine recovers and then RPMs continue to increase. I'm guessing this means not enough fuel (too lean) --- and, since I have the idle mixture at about it's best spot probably need a larger main jet. But - since I'm a total ignoramus about this stuff -- and since the carb is really difficult to get in and out - thought I'd ask before hand. Larger main jet??? Photo 1: Can't get the carb completely vertical ..... important?  Photo 2: Glove around Uni to restrict air flow  Video of bogging down (before putting glove on Uni): |
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Post by rcq92130 on Sept 13, 2014 22:09:57 GMT -5
Thanks, Jerry.
Alley sent that to me last week when I was playing with the old 24mm carb (unsuccessfully).
Before doing these fine adjustments, I was wondering if I should rejet the carb with bigger or smaller jets.
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Post by rcq92130 on Sept 13, 2014 17:31:58 GMT -5
OK I'm hoping Moat , or geh3333, JerryScript or alleyoop, will still help out 'cause i think things have changed (for the better)! New (30mm) carb is in and working. Do not yet have the new coil. Much, much better! Have not done a thing to tune, but it just might be that tuning is all that is now needed. Starts OK. Sudden WOT (on the stand) gives good, rapid, smooth RPM climb ---- up till about 5000 RPM. Then it bogs and does not want to go higher. BUT ~~~~ if I back off to about 3/4 throttle the thing get's it's legs back and accellerates suddenly to 7000 (where i stop - new piston rings). Slight pop or two when throttle is released and engine coasts back to idle. Too rich? Have 38 pilot and 120 main. I have a 35 pilot and a 120 main if those are what is needed. |
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Head gasket
by: rcq92130 - Sept 13, 2014 13:21:27 GMT -5
Post by rcq92130 on Sept 13, 2014 13:21:27 GMT -5
With "REAL" engines (i.e., not those for a sewing machine, like our GY6's!) the head gasket has coppy rings around each cylinder that crush when installed for a good fit.
The head gasket for the GY6 is just a black plastic thing. I don't see that anything 'crushes'.
Thinking about pulling the head off (for the 5th time on this ridiculous, keystone cops BBK install!) so I can lap the new intake valve in (which I plumb forgot to do).
But will I be able to re-use the same head gasket? It has zero miles on it, but HAS been used while trying to resolve the 'stuttering' problem I've had.
Anyone know?
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Post by rcq92130 on Sept 13, 2014 9:51:35 GMT -5
Thanks, Moat & GEH!
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Post by rcq92130 on Sept 12, 2014 20:08:10 GMT -5
OK. have the new 30mm pumper carb set up with 38 pilot and 120 main (that's all I have - except for a smaller 35 pilot and a huge 130 main (plus smaller mains).
Will install it tomorrow and just for yuks see what happens, though i don't expect any improvement till the new coil arrives on Tuesday.
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Post by rcq92130 on Sept 12, 2014 14:59:22 GMT -5
alleyoop Moat geh3333 JerryScript Alley, Moat, Geh, JerryScr .... or whomever Received my 30mm carb today and will install it while i wait for the new ignition coil to arrive (prob. Tuesday). What main and pilot should I start out trying?
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Post by rcq92130 on Sept 12, 2014 14:29:34 GMT -5
New 30mm carb just arrived. It was pretty stratight forward to do away with the hated "enricher circuit" on the old OEM carb --- just slipped a piece of gasket material between the "choke" body and the carb body, sealing off the 3 holes. This new carb (see photo) does not HAVE an "enricher body" -- the whole shebang is part of the carb casting. Anyone know what hoops I have to jump thru to do away with this elephant on ym new carb?  |
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Post by rcq92130 on Sept 12, 2014 14:05:36 GMT -5
I guess I don't get what the downside is.
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Post by rcq92130 on Sept 11, 2014 18:04:21 GMT -5
GEH convinced me the biggest problem with the stock exhaust is the exhaust manifold (pipe), not really the muffler.
So I bought a better (larger diameter) manifold, drilled out my stock muffler, and will soon take this all to my muffler shop to have them welded together. Easy, very inexpensive, effective.
And it fits my retro-style scoot.
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Post by rcq92130 on Sept 11, 2014 13:37:10 GMT -5
Intake is actually a bent piece of soft steel exhaust pipe ...
but I've had the thing detached from the carb the last 2 days to eliminate any filter effects. So, that's not the problem.
Wish I had another coil to test with instead of waiting till Monday for the new one to arrive!
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