Author Topic: Lost compression (Read 2042 times)

Srubey52 · « **on:** February 27, 2014, 08:37:48 pm »

Alright so iam just getting to work on my quad since I lost compression this summer. I was at the sand dunes and the quad lost compression and I looked at the carb and the intake boot was loose would this cause me to lose all compression and blow it up or just get new gaskets and that's it because the piston looks good with no holes and no slop... Need some helps thanks.

Rainman56 · « **Reply #1 on:** February 27, 2014, 09:34:12 pm »

When you say lost compression is it a little low or no compression and won,t run?A loose intake boot can make it very lean and burn up a piston on top.Possible hole in piston or even seen them break a piece of the top off above the ring by the exhaust port.

Dezsled · « **Reply #2 on:** February 27, 2014, 11:05:38 pm »

Pull the cylinder to see if the rings are stuck. What's the cylinder bore look like

LT500Kid · « **Reply #3 on:** February 27, 2014, 11:27:40 pm »

If there is low compression rings aren't stuck.

Srubey52 · « **Reply #4 on:** March 06, 2014, 05:05:47 pm »

Well it's blown up smashed the rings on exhaust side.

Dezsled · « **Reply #5 on:** March 06, 2014, 05:13:53 pm »

It happens....

If it hasn't scored the bore I'd run a quick hone and replace the piston assembly.

LT250RWV · « **Reply #6 on:** March 06, 2014, 06:08:42 pm »

When you rebuild it do a leak down test before you start it.

Srubey52 · « **Reply #7 on:** March 06, 2014, 06:54:27 pm »

Motor has never been bored out yet so iam gunna get it bored it was right at the tolerance... How do u do a leak down test?

LT250RWV · « **Reply #8 on:** March 07, 2014, 02:55:22 am »

Il post a link later

MotorGeek - Jerry Hall · « **Reply #9 on:** March 07, 2014, 07:11:53 am »

Quote from: Srubey52 on March 06, 2014, 05:05:47 pm

Well it's blown up smashed the rings on exhaust side.

Show us the piston skirt on the other side. Show us the top and underside of the piston. This piston is not smashed is has been overheated. But I need to seem more of the piston to help diagnose the problem.

Srubey52 · « **Reply #10 on:** March 07, 2014, 08:02:30 am »

The other side of the piston looks brand new.. Abd the top is like a like charcoal color I believe it got leaned out when the intake boot came loose... I will post more pics later today

GrkGuy · « **Reply #11 on:** March 07, 2014, 08:48:03 am »

are any of the rings stuck, do they move easy

Srubey52 · « **Reply #12 on:** March 07, 2014, 11:16:57 am »

Rings are stuck

Srubey52 · « **Reply #13 on:** March 07, 2014, 03:22:25 pm »

Here are the piston pics

Srubey52 · « **Reply #14 on:** March 07, 2014, 03:24:44 pm »

Another pic

GrkGuy · « **Reply #15 on:** March 07, 2014, 03:52:18 pm »

maybe they didnt check ring gap, and just ran it

Rainman56 · « **Reply #16 on:** March 07, 2014, 04:57:53 pm »

Not sure what make piston you have but gotta watch some of the cheaper piston and rings.Had a new set of pistons for an old snowmobile and the rings fit way to tight from new and had to send them back.Heard of it happening to a few others as well.

Not saying that's what caused your issues but something to watch for.

Dezsled · « **Reply #17 on:** March 07, 2014, 06:39:02 pm »

Rings have a marking near the gap, and the rings are installed with the marking upward. I'm sure everyone knows this.....

GrkGuy · « **Reply #18 on:** March 07, 2014, 09:16:50 pm »

did bike have a freash bore or hone

Srubey52 · « **Reply #19 on:** March 08, 2014, 12:55:14 pm »

Fresh hone

MotorGeek - Jerry Hall · « **Reply #20 on:** March 08, 2014, 02:14:23 pm »

Quote from: Srubey52 on March 07, 2014, 03:24:44 pm

Another pic

You have a piston overheating problem. We need to check the cooling system, the fuel system, the exhaust system for proper operation. Show me the spark plug or look at the porcelain insulator using a 2 to 5 power magnifying glass that surrounds the center electrode and describe what you see. It is not a piston to cylinder wall clearance problem. The failure is not related to the brand of piston or ring gap.

Does you bike have a spark arrestor type muffler? If so ,does it have a screen or turbine type arrestor in the muffler? What type of exhaust system do you have?

Describe how you were riding it the last 30 seconds before it quit.

I just noticed that you said you had a loose intake boot. That may have cause the engine to run extremely lean lean at anything less than about 3/4 throttle position. We still need to check the things mentioned above to make sure it does not do it again when you install a new piston.

PeeWee · « **Reply #21 on:** March 08, 2014, 04:04:38 pm »

sand is difficult to keep out even with the best of efforts. with the boot getting loose you can almost be sure sand went in the engine

Meaness1983 · « **Reply #22 on:** June 15, 2014, 05:57:29 am »

I had mine just lose compression to. I took it apart and one of the thrust washers in the top end broke. It then come past the rings a scarred the sleeve some kinda terrible. Im in the process of getting it resleeved.

Glamisrider · « **Reply #23 on:** June 16, 2014, 12:35:27 pm »

Quote from: meaness1983 on June 15, 2014, 05:57:29 am

I had mine just lose compression to. I took it apart and one of the thrust washers in the top end broke. It then come past the rings a scarred the sleeve some kinda terrible. Im in the process of getting it resleeved.

This is why you do the aluminum thrust washers for $20.

Cheap insurance.

Sorry to hear about this.

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Author Topic: Lost compression (Read 2042 times)

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