Engine Trouble will NOT run

[joeltrain]

Ive read and tried everything i can find

special thanks to Mr. Don Grubee

2010 66cc GT5 POS

A little backround. This is my second GT5. My first was great except the rear motor mount bolts sheared off leaving the chain to hold motor in place. Lots of vibration. So I decided to buy a new one as gasbike.net had sent me a discount email. 20 days later I was installing on my new Specialized Hard Rock. CNS carburetor NG. Backfire caused head gasket and bottom cylinder gasket to blow. I only realized the head gasket. Head bolts not torqued by factory. I took two off with my fingers. Put Speed carb from old motor on and sealed head, intake and exh. Did not fix lower cyl gasket. Engine very loud. Significantly less power than old motor. Ran for 1 week.

Bolt holding crank gear (clutch side) worked its way through cover and fell off inside. Tried repair on side of road but chinese hardware failure (flat/phil pan head cover bolts) stripped. Somehow I made it home. The gear must be pressed on or something b/c i rode all the way home with no bolt in it. Repaired that with old parts, and ran for several more weeks.

Having problems with fuel mixture. Engine seems to run out of gas going up big hills. After boggin it up a hill, engine goes full RPM for 10-15secs and then idle goes up and down drastically then dramatically then annoyingly and then calms down and idles. Sometimes stalls. Internets says go leaner when hot/humid. Order several jets .66,.68,.70.

While waiting for jets I discover cyl sleeve gasket leak and repair. Engine sounds much better now but mix prob is still bad. Jets do not solve problem. Order .74,.76,.78.

THEN, Riding home from corner store i reached 28mph. Fastest Ive been. Running pretty good.....

HASN'T RUN SINCE.

Tried the following to remedy:
new cdi
new performance wire
new mag coil
brushed varnish off mag coil
sanded grounds down to bare metal
disconnected kill switch
checked with voltmeter blue to black plug out 1200rpm drill = 49vac
grounds good
spark good
fuel flows from bowl drain well
plug is wet
checked magnet against old motor magnet = same
blew out carb with compressed air ALL orifices clear
installed o ring @carb intake
regasketed intake/cyl sleeve
checked mag install blue=top white=bottom
checked keyway TDC piston TDC
installed hi flow tank drain and new fuel filter
installed .66,.68,.70..72,.74,.76,.78 jets

NONE of this worked? I have a new NT new old stock carburetor coming from china. If that doesn't work, i don't know what i'm a gonna do. I can't even think of anything else to try.

 

[motorpsycho]

"Having problems with fuel mixture. Engine seems to run out of gas going up big hills. After boggin it up a hill, engine goes full RPM for 10-15secs and then idle goes up and down drastically then dramatically then annoyingly and then calms down and idles. Sometimes stalls. Internets says go leaner when hot/humid. Order several jets .66,.68,.70."

This could be caused by the float being out of adjustment. the fact that it only does this when going up hills tells me that your float bowl is running out of gas, and the angle of the carb / bike going up hill is not allowing gas to get to the main jet. Another sure fire clue that it's running out of gas is that it goes to full rpm for 10-15 seconds. it does that because it's running out of gas and the air/fuel ratio is becoming very lean before it finally runs out of gas.
check your float level and make sure that the carb is as level as possible with the bike on a flat surface.

 

[joeltrain]

That's an excellent thought, one that didn't occur to me. I bought a hi-flow tank drain valve so that should help with flow. I think i saw some post on here for the clearances on the float level. I will check that. But i still gotta get it to run 1st! Thanks!

 

[HeadSmess]

sounds like youve had fun and maybe learnt one or two things. unfortunately the biggest lesson is still to come...anyways.


psycho has the train of thought going in the right direction with the float height i say...

so thats that bit. now. prove its actually a carby issue. pull off the carb. pour a few cc of petrol down the hole. try and start it. if it runs it will rev up once then die.

that will prove if its the carb or not.

if it isnt the carb... youll be back

 

[HeadSmess]

waaaaait...plugs wet?

just thinking... plugs arent sposed to be wet

 

[joeltrain]

wet with fuel, should spark burn that off?

 

[motorpsycho]

wet with fuel, should spark burn that off?

Ummmm, yes...it's called cumbustion for a reason.
if the plug is wet at the electrode, then you do not have spark and your engine should not run at all.
if it's wet around the threads, it may be caused by too much oil in the gas.
What gas-oil ratio are you mixing it at? You are using 2 stroke oil and not regular motor oil right? (i had to ask).

 

[joeltrain]

I am running 25:1 on walmart blue supertech oil. I got my new NT carb today. I can get the float any higher than 19mm. Prev post says needs 2b 21mm. The primer pin is in the way. I read the post on NT adjustment but it doesnt really tell you what the jet size is if you buy the carb separately from ebay shipped from someone in china..lol.

I also bought a nice new two electrode shorty spark plug today. I looked all around locally and couldn't find a z4jc or a z4c. I attached pix. I've been working on this so long im starting to get burnt out!

Anyway I reinstalled the magnet and the magneto blue wire down. Keyway is at 1oclock position with piston at TDC. Blue wire to blue wire black to black. White is wrapped in tape.

SO, Electrical system is ENTIRELY new, so is Fuel. I'm gonna check all my work over again before i try to ride. If it doesn't work i think im gonna have to sell it. I've been working on this so long im starting to get burnt out!

 

[joeltrain]

magneto install pix

 

[joeltrain]

plug pix