GY6 getting spark but won't start. Wiring?

[schmidtc194]

I have a Baja Reaction 150. I just bought it from some guy (whom I'm begining to dislike) He said it ran but it needed a new automatic choke because it had broke off. After getting it home I relized it had no spark plug, no fuel pitcock, no ignition/push button. I have replaced all the above, but the wiring was all messed up and wires not connected. I have replaced everything to the best of my ability using the close but not exact wiring diagrams I have found online, all appears to be correct. I'm getting good spark and fuel. It will pop or backfire out of the carb while turning over but will not start. I also forgot to mention that I have checked the valves and they are to spec. My question is can I get good spark out of the plug and still have some wires not connected properly that would make it backfire but not start? There is a strong posiblity that I do not have the wires correct. Just want to know if this is possible. Any help on this would be appreciated.

[GX150]

Have you cleaned the carburetor? If it sat for any length of time with fuel, the passages and jets are clogged.

[SYCARMS]

Ditto: and I would expect that since you did check the valve lash all marks lined up for the timming.

TOM

[schmidtc194]

That might be putting too much faith in me. What do you mean by "all marks lines up for timing"? When we did the valves we simply found TDC and adjusted to spec. Not sure about timing though. How would I check/adjust timing.

[SYCARMS]

When you brought the engine to tdc the cam must also line up for you could be 180deg out, and if you set the valves 180deg out the engine will hardly start if at all and you will get back firing due to it being out of time. Behind the right side fan cover is the flywheel. The T lines up with the poinder on block. This may be off slightly depending on timming advance built into the cam, but the T should be close to the pointer. Now with the valve cover removed the large hole in cam sprocket should be pointing toward seat back and the either 2 small holes or lines should be parralell with the top head surface. This puts the piston at tdc and the heals of the cam lobes up. Engine is at this point in time. The reason I asked is that sometimes people set the valves with timming 180deg out or the cam sprocket skipped due to a streached chain and this will throw the timming out.

TOM

[bam41]

Here is what Tom is talking about. 1st pic is the 'T' and pointer he is referring to. The second pic is the camshaft. Large hole is at the top at TDC and the two smaller ones are evenly in line with the head as you see in pic. Hope this helps.

[schmidtc194]

The timing matches up perfectly! I'm going to do a compression check when I get off work. My next problem is where can I get parts for a 1P57QMJ? From what I have read the only difference is a long/taller cylinder and larger valves. I haven't been able to find any compatable parts online. I'm assuming the worst before I tear into the motor. Hopefully it's just a piston and rings. Does anybody know where to find parts for this style motor?

[schmidtc194]

GX 150: yeah I cleaned the carb, jets where clogged but didn't help. The motor has good spark but all it will do is occasionally backfire out of the carb and that's not very often. Going to check compression. If it's good then I have no idea. Any suggestions?

[SYCARMS]

What did you set the valves at? Were they set hot or cold? Did you soak the whole carburetor or just clean the jets ? When do you get the backfire on acceleration, letting off throttle, does it backfire when first accelerating or throughout power band. Be as specific as possible. I should be able to get parts you need but if needed I will need more info about the engine.

TOM

[schmidtc194]

I set the valves, both intake and exhaust at .005 cold. I checked the timing and with the motor at TDC with cam marks lining up with top of head and the hole in spocket at top the flywheel "T" mark lined up perfect.

I cleaned the carburetor but did not soak it. It will only backfire occasionaly while turning over, and will only do it while pressing the gas peddle about half. That's the only sign of life she shows.

I haven't been able to check compression yet, but I'm assuming this will be my problem. Will the standard 157qmj piston/rings fit the "P" motor? What about the valves? I've read the "P" has larger valves.

[SYCARMS]

When doing the compression check make sure the throttle is in wide open position otherwise you will get a false reading.Turn engine over about 5 or 6 revolutions, note how the needle on gasuge moves on each revolution then record the highest reading. In other words if the first couple revs barely move the gauge note this, also does it take all 5 or 6 revolutions to reach top compression or 3 or 4. If the reading is low 125 psi or lower then squirt some oil in the cylinder,you don't need much just a few squirts then repeat the test. I the compression rises then the rings are bad if the compression stays the same it might be valves. Repeat your tests a few times and remember to have a wide open throttle when doing the test. Let us know the results, be as specific as possible. You must remember that we are not there so the more information you give us the more accurate the diagnoses we can give you.

TOM

[schmidtc194]

Awesome. I will do the test tomorrow morning when I get home from work. I appreciate all your help and I will post my findings. THANK YOU.

[schmidtc194]

Tom:
I did a cmpression check and it was less than 30 psi, also had pressure coming out of vent on head. I took motor apart and the piston was hammered. It had scrapes on top along side. Rings were shot. The cylinder has surface scratches but no deep grooves. Should I replace cylinder? What about valves, they appear ok but I don't really know what to look for. It is the "P" motor and from what I read it has larger valves, do you know where I can get new valves? Thanks for all your help!

[SYCARMS]

I guess my first question is what hammered the piston? Keep in mind that I do not see what you see and surface scratches to you may not be to me. I would look the head over very carefully looking for abnormalties. You can put some thin liquid eg. carb cleaner in the intake and exhaust runners and see if it leaks past the valves and if so how badly.I do have 61mm cylinders for that engine with the 3 1/8 spacing of the studs. To see what you got measure diagnally across two studs center to center, it will either be 3" or 3 18". The kit I have however will require boring of the case which I can do. Give me some more specifics such as mentioned above and if possible some good pictures of the piston , head, and cylinder. Also where are you located?

TOM

[schmidtc194]

Hey guys, just wanted to update you on my Baja 150. I did a top end rebuild including; cylinder, piston/rings. I reused my head, it seemed ok. I cleaned off all the carbon build up and sprayed carb cleaner into the runners and nothing leaked. I got everything back together yesterday and it fired right up. Just wanted to thanks you guys for all your help!!

[SYCARMS]

Great to hear you got it running.

Tom

[bam41]

Sweet!