84 with compression in reverse but less in forward

sonnyhooper · 09-16-2012, 05:30 PM

So I picked up another cart today. This one supposedly had a rebuild motor but doesn't run. I have checked compression and when turning in reverse it has 75 pounds and in forward it has only 35. What am I missing? Could this be reed valves?

Doc's BoneCracker · 09-16-2012, 06:05 PM

Nope sounds to me like either bad valves or rings it has to have 100 psi no matter what to run. but best is 140 range.

1fast67 · 09-16-2012, 06:22 PM

What doc said. Or they put the piston dish toward the exhaust. Its supposed to face the intake side. Like doc said its the rings.

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sonnyhooper · 09-16-2012, 08:50 PM

Thanks guys. I just pulled the motor and removed the jug. The rings are seized into piston near the locating pins. There is considerable scoring on the piston and jug where the rings seized. So next question is what is the cause? The crank seals and bearings feel great. Can I get away with having the cylinder bored and put a oversized piston in?

1fast67 · 09-16-2012, 09:39 PM

My guess would be the auto oiler failed or simply not enough oil in the mix ratio. The biggest overbore piston is .50 so hopefully it will clean up otherwise you will have to buy a top end kit.

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Doc's BoneCracker · 09-17-2012, 05:49 AM

Did the last guy use oversized piston? if not go with .25 and yes you can get away with just piston and rings if its that new.

sonnyhooper · 09-17-2012, 07:16 AM

What is the standard bore? I think he replaced the jug it looks like a replacement. Is there any advantage to shaving the head a little?

racin161 · 09-17-2012, 07:34 AM

With the rings stuck in the ring grove and a resent rebuild I'd bet the rings were installed upside down by the past owner

Bet he never got it to run. As for shaving the head if your going to bore the jug why not cut the jug if you want more squeeze or compression. Be advised adding compression will also require the S/G to labor harder starting so all components attached will have to be in prime form. Battery-cables-grounds-solenoid and so on.

LOU

sonnyhooper · 09-18-2012, 07:39 AM

I can't remember if its bevel up or down. Why would the compression be different in forward or reverse. Could this be the brushes in the s/g making it spin faster one way? I have ordered a new piston and will have a local machine shop bore the cylinder. I have removed the oiler. The previous owner took the govenor off will this hurt it at all?

frodrummer · 09-18-2012, 08:56 AM

The govn'r off shouldn't hurt it, and shouldn't affect compression, youll just have to watch your rpms when driving.

09-16-2012, 05:30 PM	#1
sonnyhooper Getting Wild Join Date: Aug 2012 Location: minnesota Posts: 103	84 with compression in reverse but less in forward So I picked up another cart today. This one supposedly had a rebuild motor but doesn't run. I have checked compression and when turning in reverse it has 75 pounds and in forward it has only 35. What am I missing? Could this be reed valves?

09-16-2012, 06:05 PM	#2
Doc's BoneCracker Gone Wild Join Date: Jan 2012 Location: Kansas City, Mo Posts: 544	Re: 84 with compression in reverse but less in forward Nope sounds to me like either bad valves or rings it has to have 100 psi no matter what to run. but best is 140 range.

09-16-2012, 08:50 PM	#4
sonnyhooper Getting Wild Join Date: Aug 2012 Location: minnesota Posts: 103	Re: 84 with compression in reverse but less in forward Thanks guys. I just pulled the motor and removed the jug. The rings are seized into piston near the locating pins. There is considerable scoring on the piston and jug where the rings seized. So next question is what is the cause? The crank seals and bearings feel great. Can I get away with having the cylinder bored and put a oversized piston in?

09-17-2012, 05:49 AM	#6
Doc's BoneCracker Gone Wild Join Date: Jan 2012 Location: Kansas City, Mo Posts: 544	Re: 84 with compression in reverse but less in forward Did the last guy use oversized piston? if not go with .25 and yes you can get away with just piston and rings if its that new.

09-17-2012, 07:16 AM	#7
sonnyhooper Getting Wild Join Date: Aug 2012 Location: minnesota Posts: 103	Re: 84 with compression in reverse but less in forward What is the standard bore? I think he replaced the jug it looks like a replacement. Is there any advantage to shaving the head a little?

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09-16-2012, 06:22 PM	#3
1fast67 Gone Wild Join Date: Mar 2012 Location: spokane,wa Posts: 974	What doc said. Or they put the piston dish toward the exhaust. Its supposed to face the intake side. Like doc said its the rings. Sent from my LG-P999 using Tapatalk 2

09-16-2012, 09:39 PM	#5
1fast67 Gone Wild Join Date: Mar 2012 Location: spokane,wa Posts: 974	My guess would be the auto oiler failed or simply not enough oil in the mix ratio. The biggest overbore piston is .50 so hopefully it will clean up otherwise you will have to buy a top end kit. Sent from my LG-P999 using Tapatalk 2

09-17-2012, 07:34 AM	#8
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515	Re: 84 with compression in reverse but less in forward With the rings stuck in the ring grove and a resent rebuild I'd bet the rings were installed upside down by the past ownerBet he never got it to run. As for shaving the head if your going to bore the jug why not cut the jug if you want more squeeze or compression. Be advised adding compression will also require the S/G to labor harder starting so all components attached will have to be in prime form. Battery-cables-grounds-solenoid and so on. LOU
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515

09-18-2012, 07:39 AM	#9
sonnyhooper Getting Wild Join Date: Aug 2012 Location: minnesota Posts: 103	Re: 84 with compression in reverse but less in forward I can't remember if its bevel up or down. Why would the compression be different in forward or reverse. Could this be the brushes in the s/g making it spin faster one way? I have ordered a new piston and will have a local machine shop bore the cylinder. I have removed the oiler. The previous owner took the govenor off will this hurt it at all?

09-18-2012, 08:56 AM	#10
frodrummer Gone Wild Join Date: Sep 2012 Location: Savannah MO Posts: 216	Re: 84 with compression in reverse but less in forward The govn'r off shouldn't hurt it, and shouldn't affect compression, youll just have to watch your rpms when driving.

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