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Post by rcq92130 on Sept 7, 2014 16:10:30 GMT -5
So I received my 60mm BBK. The items were great - especially for the price. My assembly work not so great (must have been on drugs or something. Kept forgetting one set or locating dowels - first under the jug (take all apart again), then under head (take apart again) then under valve train (take apart again). Then last time tried to reassemble w/o slacking tensioner and ended up bending intake valve. GRRRRRR!
So get replacement valves Friday, installed Saturday, fired up. All seemed fine.
Started riding up/down local hills to break in the new piston rings. All seemed fine. Couldn't give much power during break-in, but scooter seems to have WAY more oomph.
But then after about 20 miles I noticed a hiccup or stutter. Went away. Within the next mile it got worse. Decided to turn around and get back home (about 2 or 3 miles). Within maybe 2 miles of the first stutter it was really bad. Surge ... stutter .... surge .... stutter.
Pulled over. Idle was good - nice and smooth. But any acceleration and the bucking ... surging ... faltering ... stuttering ... surging came back. Got home only at low speed and with little throttle. The impression I got was fuel starvation (gas tank is full, opening gas cap does not help).
This morning checked a few things. Spark plug looked OK (gap was in the 20s so I reset it to 32). Intake valve (the new one) seemed to have seated in a bit since valve gap was above 6mm (reset it). Only 2 vacuum lines remain - one to fuel pump (only) and one to carb (only). Both look intact. Manifold looks OK.
Started it up - started very well, idled very nicely. Hoped on, got 200 yards, turned around. Still surging, faltering, surging, faltering, can't get enough consistent power to get up to any speed above 20 or 30 mph.
Any thoughts? Fuel pump crapping out? Carb clogged? God hate me?
ps: 150 Gy6
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Post by alleyoop on Sept 7, 2014 16:17:19 GMT -5
Did you upjet your carb? If its the stock 24mm carb they come with a #35 pilot jet and a main jet anywhere from 103-107.
Or did you change the carb.
Also set both valves to .004 inchs.
Alleyoop
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Post by rcq92130 on Sept 7, 2014 16:22:34 GMT -5
I upjetted BEFORE getting the BBK ---- ended up using a 115 (i think) in the stock 24mm carb. No change to pilot jet. Was planning on revisiting all that after getting a larger exhaust manifold installed.
Scooter was running well before the BBK install with the bigger jet ... and ran well for 20 miles after the BBK install, when it suddenly went into stutter/surge mode.
Valves are set to 004 or 006 (004 passes easily; 006 will not pass)
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Post by alleyoop on Sept 7, 2014 16:27:40 GMT -5
How about your air filter what do you have on it and did you change it from what you had before. Have you adjusted the fuel ratio mixture?
Try this when it acts up surging and stuttering BACK off the throttle about 1/8 to 1/4 of an inch and hold it there and pay attention to what the motor does, A. does it speed up or B. does it just settle down.
Also does it make sounds like BRAT or POP sounds does it Backifr(POW POW) etc..
Alleyoop
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Post by rcq92130 on Sept 7, 2014 16:43:45 GMT -5
1. Some minor BRATing - just a little, but there at times.
2. Same UNI filter I had before.
3. Like i said - was riding and everything was OK. Then, at about 20 miles in it started missfiring; within a mile it got bad. So, of course there wasn't any change to the components from when it was OK till when it started acting up.
4. If I back off on the throttle it settles down ... but the max throttle at which there is no surge/falter seems to be decreasing. When this started yesterday it was OK up until maybe 1/3 throttle (in breakin period, so wasn't throttling more than that). Now it's at maybe 1/4 throttle or less. Odd thing is idle is still OK. Really, really feels like gas starvation with the surge thing.
5. Checked the fuel lines for kinks or problems, all look OK. When I installed the BBK I didn't remove anything from the carb - left the filter & fuel lines attached and just wired it to the crossmember as i dropped the engine. So didn't monkey at all with the carb from before BBK, when all was OK.
6. Any chance I have ANOTHER failed intake valve?
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Post by alleyoop on Sept 7, 2014 16:58:17 GMT -5
Great, different motor sounds tell you what the motor needs and if it is making BRAT or what I call FART sounds(hehe) is that it needs more fuel. So put it on the center stand and let it warm up at idle for at least 5 minutes then adjust the fuel ratio mixture screw. Turn it Counter Clockwise 1/4 turn at a time and wait about 10 seconds or so to allow the motor to catch up. If the IDLE goes up repeat until it does not go up and does nothing on your last 1/4 turn counter clockwise then turn it 1/8 clockwise. Then give the throttle a quick full twist and let go and see if it revs up smooth and quick and comes down to idle quick and holds. Alleyoop Here is my write to help determine what the motor needs when the motor makes different sounds: itistheride.boards.net/thread/52/motor-sounds-tells |
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Post by alleyoop on Sept 7, 2014 17:37:59 GMT -5
If that isn't enough you will have to probably get a bigger main jet, 117.5 or a 120 and make sure the pilot jet is AT LEAST a #35 because you may need a #38 Pilot jet. The Uni lets a lot of air in and it is to much air and not enough fuel.
Alleyoop
Just to give you a reference, I have a 62mm and K&N filter it takes a 122.5 main and a #38 Pilot.
A 125 was to much fuel it will run with a 120 but on the edge of lean.
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Post by rcq92130 on Sept 7, 2014 18:01:18 GMT -5
Here is a (blurry) pic of the spark plug this morning. Does not show well ---- plug had a slight tan tint (DEFINITELY not white). Thought it looked sort of "OK"  |
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Post by rcq92130 on Sept 7, 2014 18:08:13 GMT -5
I appreciate the help and (of course) will do as you recommend. But i like to learn and (if you don't mind) have a few questions
1. Idle jet. Idle is way off - have it set to 2000 RPM because the engine dies at less than that. Have planned to revisit that after I get the larger exhaust in place in a day or 2. But since the idle at 2K is nice and smooth, and the idle jet will not do much at higher engine load, is it correct I should start to work on the open throttle problem by adjusting the idle jet?
Have it set now at 2 turns out. Three weeks ago or so had turned it very far out (looking for a place where RPMs started to drop, which they never did), and whil riding the needle actually FELL OUT (with the spring). Luckily it was lying down below the starter motor. That's why put it back in, set it at 2 turns out, and left it till I have the final exhaust on. Kind of a little worried of the thing falling out again and me not being so lucky it wedges on the engine for me to find but falls on the street somewhere.
2. Would it make more sense to put a larger main in? I have a 120, a 125 and a 130.
3. This is the biggie: why would it run very well for 20 miles, and only THEN crap out?
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Post by rcq92130 on Sept 7, 2014 18:27:02 GMT -5
Oh - just saw your second response.
OK - I'll throw in the 120 main and see if that solves the problem.
But why would it run very well for 20 miles and then suddenly act up?
I assume the pilots have a stamping on them somewhere. Will look.
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Post by alleyoop on Sept 7, 2014 19:08:48 GMT -5
You see the plug on top and around the top of the threads that is a lean condition plug. It should be a little dark. I personally do not like plug chops and never bother because if you do not do it right the color will change on you in a minute.
I go by throttle response and hearing the motor, but then again I am a motor head. I can tell just by the sound and how it revs if something is not right. For intense if you twist the throttle and the rpms are slow to drop back down to idle it is to LEAN, If they drop down to idle and it keeps on dropping and bounce it is to RICH. Also if the muffler sounds throaty it is to rich if it sounds tinny it is to Lean. A properly set mixture and setup you should be able to twist the throttle the rpms climb fast with no hesitation and drop back down to idle .
As far as why it happens after so many minutes and or miles is the heat, things start to expand and if it is running lean in the first place makes it worse. So now things get hotter and your valves may not be sealing good as when cold sucking in less fuel and air due to loss of some compression. But try the 120, as far as the markings a lot of them are not marked.
Now since you say that it will idle at 2000k otherwise it will die then your IDLE JET is most likely to small as well.
To find out do this:
The Fuel Ratio screw will not fall out until about 6-8 turns out BUT with the proper jet you would only be out anywhere from 2-3 1/2 turns out. If you have to turn it out further than that to get a good idle then the pilot jet is to small. On the other hand if you turn it clockwise and close it or it does not kill your motor when you have 1 full turn to the closed position then the pilot jet is to big.
Alleyoop
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Post by rcq92130 on Sept 7, 2014 19:09:37 GMT -5
OK - put the 120 main in and did a quick test.
Still sputtering on acceleration. Might be marginally better - don't yet know. Will do longer ride tomorrow and see if there seems to be a real improvement.
Checked the idle jet ---- 32. So I need a 35 or 38.
Do you know if regular motorcycle shops generally carry jets for these little things? Have bought everything online so far ... for the idle jet I'd rather just find some place local and be done with it. but not any scooter places very close by ... motorcycle yes.
ps: thanks for the explanation!
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Post by alleyoop on Sept 7, 2014 19:12:23 GMT -5
Ah, small pilot jet that is why the plug is showing not dark around the edge and the tip, get a #35 or if you have one put that in that should fix your sputtering until the main jet kicks in.
A 32 is like for a modded 50cc motor.
Alleyoop
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Post by rcq92130 on Sept 7, 2014 19:14:55 GMT -5
OK - will look for scooter shop tomorrow unless you think a regular motorcycle shop would have these (several of these close by; not any scooter places close by).
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Post by alleyoop on Sept 7, 2014 19:23:13 GMT -5
Most motorcycles have kehin carbs so take your pilot jet with you and ask if they have a #35 like that one. And once you get your performance muffler and what not you should be good. The piping and muffler helps to exhaust it out faster and more and will help on the top end for a couple mph more. But the jetting will be tunable for any little twicking. You won't know about the main jet until you get it past the low end and able to run it at WOT, any problem in the midrange you can always adjust the needle, but the bottom end will be good with the #35, You will get it to idle below 2000k.
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..BAD TO THE BONE..