YM 1700 hard starting

B man · Feb 6, 2019

Finally got the compression testing tool, and the verdict is....... got to do a head job. 200# was all I could get out of it, at least the cylinders are even, within a pound or two. Stinks having to work on it with a small budget, but I am learning all about the motor end.

thepumpguysc · Feb 6, 2019

" a head job"?? Don't u mean an engine overhaul??
Whats the head have to do w/ low compression??
UNLESS the valves were set wrong, throwing compression out before its time..
The PISTONS & RINGS make compression..

normde2001 · Feb 6, 2019

200 psi compression, both cyls after a ring job. You need to start from scratch and check everything, unless something wrong with test procedure..

careyo63 · Feb 6, 2019

Both low with the same amount of pressure sure sounds like a Valve problem. Esp. New rings. When you pull the head I'd be looking at the Exhaust valves hard and check they are seated. Won't be surprised if they're not......

clemsonfor · Feb 6, 2019

Yea you already built this thing? Either your cylinder liners are huge and wallowed out (I don't remember if you replaced them bit I was thinking not) , or like Pump guy said your valves are seriously out of wack or your linkage in the head for comp relealse is hung open under valve cover you missed something or there was an assembly problem.

clemsonfor · Feb 6, 2019

I'd pull the valve cover and check valves first. Before I tore anything down

careyo63 · Feb 6, 2019

#70. Valves working correctly he stated and the Decompression linkage? Didn't say he checked the Adj. though. so that could be a problem.

Jtullis13 · Feb 7, 2019

I would check the decompression linkage first, that's easy, and then dig further if the problem persists

careyo63 · Feb 7, 2019

#70 B man
Good air flow in and out. Lower end is done also. Head looked good, valves doing what they should. Decamp working correctly. Got to check the injectors. Then I guess the pump would be next. Should be like new then. I’m like you guys, compression, air, (fuel?) should start. Will keep at it, kinda bullheaded about things

Spelling error and I'm fairly sure he was meaning to say Decomp. Not decamp.......
I'm still guessing that's the problem. Exhaust and Decomp.. But the intake valves open or not seating causing the same amount of loss and low pressure is very doubtful. So just just a drop in the bucket guess is why I say Exhaust or decompression. But the H-Gasket could be a lot thinner than the old one causing the V-Adj. to change dramatically..

winston1 · Feb 7, 2019

#1 post: "YM 1700, new head gasket, new 2kw starter, will only start with wide open throttle (sometimes) usually with a little ether. What in Samhill is going on with it? TY!"

Could be broken piston lands.