Puch Won't Fire No matter what

Brandon E /

77 Puch Newport,

2hp Engine

I have absolutely no clue what is going on. It has fuel, spark, and compression, but still will not run. It won't even fire or backfire or anything, even with starting fluid sprayed in the spark plug hole. It's got a brand new spark plug with a big fat spark. If the spark were any bigger, it would solve california's energy problems! It's got enough compression to make the clutch lock mechanism slip. Even if the timing were off, it would backfire or something wouldn't it? But it doesn't. I am dead positive that it has spark. I've checked it upwards of 10 times in 15 minutes. Earlier today it would run and then kill if it went from full throttle to idle too fast, and then wouldn't start again for a few minutes. I cleaned the carb thouroughly, but, like I said, it won't even fire with starting fluid in the combustion chamber (directly sprayed into the plug hole and then the plug quckly put back) and I am VERY MUCH DEAD CERTAIN that it has spark. Watching it while grounded on the engine block, it is very consistent and fat. The compression is definitely there. This one is racking my brain.

Completely out of ideas:

Brandon E

Re: Puch Won't Fire No matter what

SteelToad /

When you cleaned the carb out, did you clean out all of the air passages, and

not just the fuel. I'm just guessing (and wildly at that) but if you have spark,

compression, and fuel, the only other thing you should need is air.


Brandon E /

Actually, I think I may have just found the problem, the cylinder head is loose! I don't know why it had compression, but it did. And worse yet, it feels like the head bolts are either stripped or the gasket has a lot of compressing to do. Does anybody know the torque specs on a Puch motor? (2 hp)

Found the torque specs.

Brandon E /

I just found the torque specs and they're only 7 lbs. Hope I didn't already overtighten them! Uh-oh!

Praying that I didn't screw up,

Brandon E

Re: Puch Won't Fire No matter what

moped warehouse of New Jersey /


Go back to the basics. When was the last time you had this moped running well? What has changed scince then? What work have you done to it since that time and what if any effect did that work have on it?


The Moped WareHouse


Re: Puch Won't Fire No matter what

Brandon E /

The last time it was running well was a few days before I started having all of the problems. I had ridden it 20 miles almost full throttle the whole way. All I've done to it since then was clean the carb and replace the spark plug. I didn't have any problems before, but I've probably ridden it a total of 40 or 50 miles at most since I've owned it. It has over 6000 miles on it, though. I also put a biturbo pipe on it as soon as I got it. I remember having to force the pipe about an inch and a half sideways to get it to fit on the bracket near the back tire. Would the sideways torque it puts on the cylinder do anything? I discovered the head was loose when I sprayed starting fluid into the spark plug hole and and tried to start it. A puddle of oily gas formed on the floor under the area between the cylinder and head, so I know it's a problem with the head and cylinder being loose. I'm gonna take it all apart tomorrow.

Brandon E

Re: Puch Won't Fire No matter what

vanilladog /

The loose head thing sounds like it would screw things up badly. I tighten the bolts on my Puch Korado by hand, and estimate the torque, but I have been doing this for many years, and know pretty much how much pressure I am applying at any time (years of fixing mopeds, motorcycles and working as a copy-machine technician). If you have a really good, white/blue spark, then it should fire by all means with starting fluid in the cylinder unless it is loose, or totally out of timing. If you get it to fire on the starting fluid, but not to run by itself, do not underestimate the power of removing, opening and boiling the carbeurator in a pot of water to clean it out thoroughly. I have saved many a motorcycle and moped by boiling the carb clean.

'Nilla Dog

Pulled the engine apart today

Brandon E /

Well, I pulled the engine head and cylinder off today, and I discovered a few things:

1. Man, that was easy!

2. The threads in the crankcase for the cylinder studs were still there and looked good, but there were aluminum shavings on the studs from the crankcase.

3. Two of the studs came out with the nuts on the head, and just the nut came out on the other two, is this a sign of worn threads?

Thanks for your help,

Brandon E

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