[Jennghigh]

Okay i'm not new to the forum but this is a new thread for the same bike i have been working on; the other is "ignition issues". So i quick run down on what i have done and whats going on: New battery, new coils, new plugs boots and wires, new ignition switch and start/kill switch, starter relay, all 4 main fuses (glass). so the starting issue is not my biggest concern. So aside from all that i am getting spark and it spins and turns the engine over freely no weird noises or smoke or smells. yet the bike will not start. In the process of diag i verified (per my printed out service manual) i was getting spark, correct resistance on plug boots and wires and coils i also reset the timing it was off. so if ive got fire, fuel and air all im missing is pressure. Might i say catastrophically so 60psi on both sides. Im in northern louisiana and our weather has been trash the last couple months so its been anywhere from 34-70 degrees f at any time. So i have the bike in my cellar it isn't fully enclosed so it stays cold got a space heater that works wonderfully to heat up the bike.

I saw somewhere if compression is low its more often the valves, then frozen piston rings but the engine needs to be warm, hard to do when it doesnt run (space heater). So go the temp up checked my compression dry 50-60psi on either side. warmed up with a little penatrating oil got it to 70-90psi (only happened once). Since the oil helped most of what i read said that would indicate valves. So took the heads off took the valves out lapped them put the heads in my ultrasonic cleaner (they were horrible when i took them off and i have since been told they're normal trash now) so new head gaskets new valve seals (obs i did both sides) put it all back together hit the start button same old same. Im beyond mad at this point i get my compression tester back out and check my readings 60psi on both sides wet or dry!!!!!! i phone a friend he comes over (15yr mechanic im only a 3yr) and he is checking everything over. He notes that the pressure is consistently low 50-60psi no flux and says its a freak occurrence no matter how many times you check it compression is staying 60psi tops.

NOTE: never done valves before on anything watched a few youtube videos and read a photo step- by-step procedure guide i thought i did okay

NOTE: i blew out all the trash and oil/water

So where is my missing 120psi going??? i dont hear any noises like i said earlier; and one would like you would hear 120psi go by on both sides. The guy i had come over did say that the pistoon is nice and snug he couldnt wiggle it around any. So i have no idea what to do now with it being consistent he doesnt think its the rings because there should be some flux in pressure in the cylinders just like in cars. Any help and ideas would be greatly appreciated im over 1000usd in this bike and it still doesnt run and im at the end of the road ( i was fixing it to sale to a friend) im not going to tear down the engine to do the pistons and have someone hone the engine. I took the heads off and poured 91% alcohol in the head to see if the valves were leaking w a little die for color and they held over night. I didnt see any cracks or fractures when i was doing the valves and i didnt know to look for any either.

 

[murrayf]

do a leak down test and see what you hear

could be your gauge could be a jumped timing chain

 

[murrayf]

another thought what head gaskets did you use

a lot of them cause problems but you will see that show up with a leak down tests

if they are bad just do teh test with teh rad cap off

 

[Jennghigh]

another thought what head gaskets did you use
a lot of them cause problems but you will see that show up with a leak down tests
if they are bad just do the test with the rad cap off

I got gaskets from 2fastmoto they look and felt similar to the ones I took off. I'll have to look an see about a leak down test. If it's an easy fix I'll do that but otherwise it's new engine time. I was fixing it for a a friend and he has agreed to a new engine and I'll part out this one.

 

[Sidecar Bob]

Any engine you find will be as old as this one and just as likely to have problems so it might be less work to fix this one.

When you check the compression are you holding the throttle fully open? If it has to pull past closed carb butterflies it will read significantly lower than specified (the choke has to be off too).

 

[Jennghigh]

I did not try it with wide open throttle but one head is off at the moment so the carbs are off. do i need to put the head back on and check it w the carbs off?

 

[Sidecar Bob]

I'd leave the carbs off and try the side with the head on. If the reading is in spec you've probably found the problem and if it is still low the next step should be trying a leakdown test on that cylinder.

There are 3 likely causes of low compression:
1) piston rings not sealing - if it hasn't been run for a few years it may just need to run for an hour or so to free them up
2) one or more valve not closing properly or not sealing - double check the clearances and make sure you check at TDC compression, not TDC exhaust. Also, when you lapped the valves did the valves themselves get shiny all the eay around or did one side stay dark? (this indicates a slightly bent valve).
3) blown head gasket

 

[Jennghigh]

Well i cant say if its number 1 because the problem is the bike wont run, so i cant run it for an hour to get the rings free.. 2 i did do the valve adjustments per the manual w it at TDC compression; and yes shiny all around on seats and valves and 3 cant be blown if they are brand new in a non running engine
and i tried to do the compression on the head installed but my battery is down from sitting so ill have to put it on charge to see if my reading changes

also i found this post ill give a go: Dan's Motorcycle "Leak Down Test" seems pretty good
{" The test is simple. Apply air pressure to the sparkplug hole and listen. You will probably have to take the exhaust pipe and carburetor off plus remove the oil fill cap. Other then that, just listen. You will need at least fifteen or twenty pounds of air pressure. Higher pressure will make the sound louder but too much and you will need to lock the crankshaft to keep the engine from turning. A hissing noise at the carburetor manifold indicated a leak at the intake valve(s). Hissing at the exhaust, leaking exhaust valve(s). Hissing at the oil fill or at the engine breather tube, leaking past the rings.

For air pressure you can use a fancy spark plug hole attachment or just a rubber tip on a blow gun. You might need an extension for these hard to reach plugs too."}

 

[D-Fresh]

Hey, Jennghigh,

Thanks for the link. Looks like there may be some good info in there but i only did a quick fly by.

I'm embarking on a similar journey, see attached pics. The rusty side had 15 psi, the carboned up one had 60 psi.

Hope you figure out your issue.

Cheers

 

[Jennghigh]

Well I don't think it's going to be the valves so I'm just replacing the whole engine there is a seller on eBay that's got one at a good price the draw guy buying the bike wants me to put it in so no more rat chasing for me. I guess I'll just part this one out and scrap what I can't sell

 

[D-Fresh]

I may be in the market for some of your parts, i just discovered the end of the camshaft with the water pump is broken off... DANG! ? Who knows what else i'll end up needing if i decide to fix this one, still deciding.

 

[Jennghigh]

Well just message me if you do!