Full tuning of carb, off By seanstr (Read 2,223 times)

[elcamino121]

I'm watching, just nothing to contribute as your doing great!!

[seanstr]

I found out that my compression had changed. Used to be at 210 which is high. Now it's at 90. So I took off the valve cover and checked the valve clearance at Top Dead Center. Still set correctly .004. So I must have a piston ring issue? There's no smoke so I'm confused.

Do one change and check results.

[elcamino121]

I'm not sure if this will work on a horizontal engine.

We would put a couple of spoonfulls of oil in the cylinder and recheck compression.
The oil helps make a temporary seal if there is excess clearance or worn rings.

Again, just my experience, others may chime in..

[cyborg]

Several things can cause low compression,,Camino gave you a good bit of advice but if there's no smoke I'd put my bet on a valve going bad,,,,take off the belt cover and get a wrench on the variator nut and turn the engine over slowly with the plug in and snug when you feel it come up on tdc listen for hissing,,,or tthe he head may have worked loose and the gasket is leaking or you may have run the compression test wrong,,,90 psi is really low to have decent fire and power

[jct842]

Good reasons to not run wide open!

[seanstr]

May 22, 2017 7:14:50 GMT -6 cyborg said:

Several things can cause low compression,,Camino gave you a good bit of advice but if there's no smoke I'd put my bet on a valve going bad,,,,take off the belt cover and get a wrench on the variator nut and turn the engine over slowly with the plug in and snug when you feel it come up on tdc listen for hissing,,,or tthe he head may have worked loose and the gasket is leaking or you may have run the compression test wrong,,,90 psi is really low to have decent fire and power

I will try those ideas next, thank you

[seanstr]

Before I try this I had thoughts. If the head is loose wouldn't I see oil drips?



Do one change and check results.

[seanstr]

May 22, 2017 7:14:50 GMT -6 cyborg said:

Several things can cause low compression,,Camino gave you a good bit of advice but if there's no smoke I'd put my bet on a valve going bad,,,,take off the belt cover and get a wrench on the variator nut and turn the engine over slowly with the plug in and snug when you feel it come up on tdc listen for hissing,,,or tthe he head may have worked loose and the gasket is leaking or you may have run the compression test wrong,,,90 psi is really low to have decent fire and power

Another question. When you say I could have run the compression test wing. What could I have done that would cause poor test results?

[seanstr]

I think you're right I did it wrong. Not wide open throttle. Thank you. I forgot to do that.
Do one change and check results.

[seanstr]

Compression 180 I worried for nothing.

Do one change and check results.

[seanstr]

Ok I'm having bogging at 45mph again. It's fine from idle to 3/4 throttle. Then bogging. I have to be at 45mph.

If I lean out the needle clip going up gets worse. If I richen the needle, going down, it's better but not enough. So I got a #106 and a #107 but the threads were different by just a little bit. I got a die to and cut it to the correct threads.

Ok, I stick in #106. It's worse. I know I need to go up one size but all the kits go from 105 to 108. That's too much.

I tried just a washer on the needle clip to get a little bit richer. Didn't help.

If all the kits are like this for do I fix this?

Do I then have no choice but to go uni filter and then start at 110 main jet instead?


Also why is tuning the carb such a pain.

Do one change and check results.

[rks]

After hundreds and hundreds of posts on your threads, and literally thousands of views, I think you have a lot of heads spinning.....I know my is. I mean no disrespect towards you, but think it's time for you to throw in the towel. There is no way a 107 should be to big, if the air filtration system is functioning properly.

Here is what I would suggest......Get a new carb, they are dirt cheap.....like this one 150cc carb
You may have to adjust the idle mixture a bit.......but after that leave it alone. You should be able to run at least 50 without any problems. If not, it isn't the carbs fault.

[seanstr]

I think I know why I cannot get the carb tuned correctly.

I am currently running a #105 main jet with the needle clip on richest setting, all the way down. It bogs from 3/4 to WOT. I had a #106 but had different threads cut into it. I could find a kit that had #106, # 107. So, I re-cut the threads to fit, but,... it's obviously leaking so that won't work, yes?

I have ordered just #106 and # 107 that is supposed to fit.

Do one change and check results.

[seanstr]

I have learned a lot.

Main jet

The diameter of the inner intake going towards the engine (not the air intake) times a constant. Slightly less than 4 to 5 is preferred.

Example. My original carb was a 28mm and the jet was a 110

28 x constant = 110
Constant = 110/28
Constant = 3.928571428571429

My current carb intake is 24mm

24 x 3.928571428571429 = 94.28571428571429 so main jet size is about 95. I only had 100. I can now get to 50 mph. Increased from 105 jet and 45 mph.

Pilot jet.

This is controlled by the needle clip and air/fuel mixture

If you turn in clockwise and it doesn't shut off engine you need to go down a pilot jet size. To get good from idle to 1/4 throttle adjust air/fuel mixture. The 1/4 - 3/4 is controlled by needle clip. Start richest and adjust from there.

Idle

The air/fuel mixture and the idle screw do all the adjustments.


1. If it surges ahead your Lean
2. If it stumbles and recovers your Rich 

Now depending on where in the Throttle position this happens Different settings have to be done:
1. If it stumbles as your starting off - Adjust your Air/Fuel Mixture
2. If it stumbles in the mid range - Adjust your Needle
3. If it stumbles at WOT - It could be your Air/Fuel Mixture or you may have to Re-Jet. 
Alleyoop

Engine number XS1P52QMI-3

Vin RFGBS1HEXDAXW0275

29 x 20 x 18 needle bearing
29mm x 15mm x 6-7mm outer bearing

Belt 824 x 20 x 30
13 gram sliders

Main jet #100
Needle lean for above 60
Needle rich for below 60
Pilot jet #35

To check if the pilot jet is either to big or to small test it:

To check if the pilot jet is to big:
1. Turn the Fuel Ratio Mixture Screw CLOCKWISE until it kills the motor.
A. If it is all the way in and it did not kill the motor THE PILOT JET IS TO BIG.
B. If it kills the motor when there is about 1 FULL TURN before closed YOU HAVE A GOOD PILOT JET SIZE.
C. If you get a good IDLE and good starts when the FUEL RATIO SCREW is MORE than 3 1/2 turns out you have to SMALL OF A PILOT JET. YOU need the next Size Pilot JET.

A good setting with a good size pilot jet the screw should be out anywhere from 3 1/2 to 2 turns out from the closed position.

All this info is from others.

Do one change and check results.

[seanstr]

I cannot get it up past 45 with the #105, tried the #100 and #95. The # 100 does the best and I can get to 50mph. It's as tuned as I can get it without fuel injection.

Do one change and check results.