The Matrix: Rebuilding By runningslow (Read 25,964 times)

[sprocket]

Possibly Keihn... they are thousands of counterfeits from China...Well if it isn't gas then it is spark...

Perhaps a bad pick-up coil? They can start to go bad and will idle but as soon as you ask it to perform faster it fails.. also a bad ignition coil or weak CDI...even a problem with your stator...

Don't want you opening more cans of worms but they could all be implicated...

[Alleyoop]

If you spray Carb Cleaner in the PILOT JET hole and Spray comes out byt the tiny holes by the butterfly THEN I think the problem is the Diapghram is NOT raiseing the Needle out of the Jet when you twist the Throttle. To check that Put the carb together and Blow Air into the Slot on the Carb on the Air Filter Side the Slide Cylinder with needle should RISE. If not that would cause your problem. You twist the Throttle which opens the BUTTERFLY to let in air and more gas but no more gas gets sucked in because the needle is NOT being raised.

I personnally would just get a NEW CARB for the $30 bucks they work great.
Alleyoop
First Spray into the Pilot Jet and see if Spray comes out of the Tiny holes by the butterfly.


Then check if the Diaphgram raises the Needle(WHICH I THINK IS THE PROBLEM):

[runningslow]

Alley, when I spray into the pilot jet, I do get spray out by the butterfly. I'll have to get myself a can of spray air and see if the needle raises.

Not something I'm going to use frequently, but it should be good to have on hand..... I just bought a compression tester from Harbor Freight.
www.harborfreight.com/quick-connect-compression-tester-95187.html
So, I'm going to check compression in the morning. If compression tests good, I'm going to try and verify my timing again. If timing seems to check out, I'll probably just order a new carb.

If compression doesn't check out... well, that's something I'll deal with when the time comes.

[runningslow]

Jan 27, 2012 18:23:55 GMT -6 sprocket said:

Possibly Keihn... they are thousands of counterfeits from China...Well if it isn't gas then it is spark...

Perhaps a bad pick-up coil? They can start to go bad and will idle but as soon as you ask it to perform faster it fails.. also a bad ignition coil or weak CDI...even a problem with your stator...

Don't want you opening more cans of worms but they could all be implicated...

I know there's a chance it could be a counterfeit Keihn, but I'm pretty sure its authentic. My scoot may have been way overpriced, but most of the components are on the high quality side.

I have a nice spark, so I'm not convinced that will be the problem. However, you may be right.

Right now, I'm convinced the problem is timing or compression.

[bcgreatness]

my honda 250 has a keihn carb, anyway, i wish i could get a hold of your scoot, if it were timing, i could get it right, but its a long ride to get to you. i take it you have not used your compression tester yet, when you do, look for compression between 100-125 psi, too much lower then 100 is very bad and anything over 125 is not bad at all but alot of compression. i highly doubt you will get over 120 compression. if you get a 300 psi reading, then your gauge is broke

[runningslow]

Ok. Compression tests yielded a best of 75psi.

However, I think I've found a source for a new head gasket.... looks like I'll be pulling the head again, but at least this time, I can do a better job of getting TDC.

[sprocket]

Engine has a leaking valve, shot gasket or the rings are worn. I have never seen a GY6 which would run under 90 psi...

A good GY6 engine should get over 150psi on a hot & wet compression test.

[bcgreatness]

Yeah, 75 isway 2 low. Hot & wet... wait, am i still on the scoot forum?

[boosthb]

Feb 4, 2012 9:08:57 GMT -6 runningslow said:

Ok. Compression tests yielded a best of 75psi.

However, I think I've found a source for a new head gasket.... looks like I'll be pulling the head again, but at least this time, I can do a better job of getting TDC.

Hey brotha I too have the same engine I got it from Scrappy Dog scooters and the I checked the compression it was at 175psi. yours seems to be too low. While checking compression did you have the throttle opened all the way cause if not it will read low.

[runningslow]

Feb 6, 2012 0:19:09 GMT -6 boosthb said:

Hey brotha I too have the same engine I got it from Scrappy Dog scooters and the I checked the compression it was at 175psi. yours seems to be too low. While checking compression did you have the throttle opened all the way cause if not it will read low.

You've got a point. I missed the step in the instructions about turning the throttle. I was only checking compression from turning the engine over with the starter. I'll check compression again tonight before I order the gasket set.

That being said, this engine has a few thousand miles on it and the head I'm using has over 8,000K miles on it. Not to mention the head gasket is questionable at best, since I was trying to re-use an old one. Leaks are very possible.

I may just go ahead and order the gasket set. That way I can pull the head again to absolutely verify TDC.

[sprocket]

Use copper gasket spray on the new gaskets.. follow the direction on the can to the letter...

Open throttle will give you consistency.. not sure what the impact is on a GY6

[runningslow]

Feb 6, 2012 13:51:22 GMT -6 sprocket said:

Use copper gasket spray on the new gaskets.. follow the direction on the can to the letter...

Open throttle will give you consistency.. not sure what the impact is on a GY6

I've got a can of Permatex copper ready to go!

Sprocket, when replacing a head gasket, do you have to change the base gasket, too? I'm just worried about screwing something else up while pulling jug off the piston.

[sprocket]

I would do both gaskets...and you need to torque the head bolts...criss-cross and retorque after 100 miles...

There is a huge amount of variation on the torque..some use 16 ft/lbs.. other go as high as 25 ft/lbs

www.buggydepot.com/buggy-tech-center/read/150cc/0/11/gy6-camshaft-installation-guide.html

[runningslow]

I quit. Changed head gasket. Compression went up to about 90.

Sent from my MoPho using the ProBoards App

[bcgreatness]

you quit? dont give up just yet. theres got to be a reason your getting low compression... maybe the gauge is broke? i would try to get a second opinion before your call it quits. i want to see that bike on the road!