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Post by 190mech on Apr 19, 2010 16:07:41 GMT -5
Yea,I've been eyeing a big chainsaw carb for my scoot...
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Post by Reign on Apr 19, 2010 16:37:36 GMT -5
You sure its not just an issue with having that giant of a tire on an engine that wasnt made for it?
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Post by 90GTVert on Apr 19, 2010 18:28:23 GMT -5
I checked and the clutch : tire is 11.125 (11 1/8 turn) to 1. the tire isn't so big that it would kill performance. This thing has always ran like this. It may not be helping, but it's not doing all of this. I'll post some details in a bit, gotta get back outside before it's dark. My headlight quit working. Man this thing is junk.
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Post by 90GTVert on Apr 19, 2010 19:07:58 GMT -5
O.K., here are more details...
8g rollers = 6850 RPM, 1/4 mile = 35MPH 6.5g rollers = 7250 RPM, 1/4 mile = 35MPH 4.5g rollers = 8000+ RPM, 1/4 mile = 35MPH
I tried 2K clutch springs and heavier contra springs. Those just made the revs even more riddiculous for the speeds it does. It doesn;t seem to matter what I do, it doesn't wanna top 35MPH. I could tuck in and find a hill or even give it a 1/2 mile I guess, but 35MPH is sad for 1/4 mile regardless. I really wish I knew what some other GY6 50 final drive ratios were.
This thing is flat out embarrassing with the loud exhaust. It sounds good, but it doesn't run like it sounds. I made a quick video after my last post just to show you how bad it is. The "fly by" is at 30-35MPH making all that noise. I should just paint it rainbow colors and wear a red nose and giant shoes when I ride it...
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Post by Fox on Apr 19, 2010 19:19:09 GMT -5
It's struggling pretty hard.
Have you tried a regular sized tire/wheel?
I have 3 50cc engines in the shop. I'll get you the ratios in a bit.
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Post by 90GTVert on Apr 19, 2010 19:32:39 GMT -5
I used to have a regular sized tire and it did the same thing basically. It might be slightly better or worse one way or the other, but that's not the whole issue. I would greatly appreciate some other ratios to compare to!
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Post by 190mech on Apr 19, 2010 19:37:52 GMT -5
Sounds like the ignition timing is verrry late,does the ignition advance with RPM?Can you slot the stator plate to bump up the timing??My "nickels worth"!! More questions,Is there timing marks on the flywheel and case? If not ya need to make some (TDC and 10degrees BTDC) Then check it with the timing light,,
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Post by Fox on Apr 19, 2010 19:45:43 GMT -5
Okay so I have two Tank engines and one from JMStar (Jonway) out there.
The two Tank engines were exactly 11:1 11 turns of the clutch bell to 1 revolution of the output shaft/rear axle
The JMStar was 11.2 :1
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Post by 190mech on Apr 19, 2010 19:50:05 GMT -5
Brent looks like we all want to see this thing go!Just checked the Honda Passport70 factory service manual and the ignition timing is 15 BTDC at idle and 30BTDC at 3100 RPM,hope this helps!
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Post by Fox on Apr 19, 2010 19:50:37 GMT -5
Sounds like the ignition timing is verrry late,does the ignition advance with RPM?Can you slot the stator plate to bump up the timing??My "nickels worth"!! More questions,Is there timing marks on the flywheel and case? If not ya need to make some (TDC and 10degrees BTDC) Then check it with the timing light,, The 4T's have T and F marks.
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Post by 90GTVert on Apr 19, 2010 19:56:33 GMT -5
Thanks. I assume neither of those were absolute turds? lol
There is a T (TDC) and an F after it on the flywheel. Timing is on the F @ 2000 RPM or so wherever it was idling. It was 2 degrees closer to T according to the inductive timing light when I modded the pickup. The stator plate on these things can't really be moved.... they don't really have a plate like the 2Ts. IIRC timing isn't suppoed to be on the F at idle, I think it was supposed to be there at a higher RPM. I'll check some manuals.
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Post by 90GTVert on Apr 19, 2010 19:57:46 GMT -5
Damn, I'm as slow as the SunL getting a post in.
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Post by Fox on Apr 19, 2010 20:03:31 GMT -5
Thanks. I assume neither of those were absolute turds? lol No the JMStar was a great engine. It went 35-40 on flats and 45-50 downhill stock. It went for 18,000 before a bearing started clunking so I replaced the entire engine with a Tank engine and it performs exactly the same as the JMStar engine. (Same carb) There is a T (TDC) and an F after it on the flywheel. Actually the F comes around before the T. The flywheel spins clockwise. Question: What color is the spark plug?
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Post by 90GTVert on Apr 19, 2010 20:05:05 GMT -5
Maximum advance in F position 13 degreees +/- 1 degree is all the manuals I have say about timing. Well yeah, F is before it timing wise... sorry, I was kinda stating it as I read right to left. lol
The plug is light tan color. Looks about right. I tuned the main jet with the tach getting the highest RPM as well as seat of the pants. I really don't think it's a carb issue... I've had 3 carb on this thing and it's always slow as hell.
I'll go fire it up and get some timing readings hopefully.
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Post by Fox on Apr 19, 2010 20:14:50 GMT -5
How do you tune the main jet?
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