Question about 1987 Yamaha SDR

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Bravo 250 I have an old 86 bravo engine that i am going to try to mount in an 85 citation, The rings are good but one side of the piston is scored fairly deep, what could be causing only one side to score? i want to fix the motor on the bench b4 it goes in the sled

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Can be from seizing due to overheat or lack of oil...
best replace the piston and rings

Posted on Nov 01, 2009


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Posted on Jan 02, 2017


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Smokes alot and may have gas in the oil

You likely have broken piston rings. If so, the cylinder walls may also be scored (gouged deep) from the broken pieces. Gas may be leaking by while it sits and it's not running. It likely means motor work - often a "short block", the main part of the engine would need replacing. It may be cheaper to buy a used motor, but only buy one with the same make and model number as mounting and drive shaft will be different for others.

May 08, 2016 | Garden

1 Answer

Oil leaking out of carb no power on aceleraton

Sounds like you have some rings broke. Does it smoke when running. Broke rings especially the oil ring lets oil get out of the crank case and run out the exhaust and carburetor. This oil is burning with the gas and burns very poorly, also you have probably lost most of the compression which will make it run poorly. If you are mechanically inclined you can replace the rings fairly cheep. Of course you will have to tear it all the way down to get the piston out. Don't run it again because you are running the risk of scoring both the piston and the block. This of course will ruin the engine. You have a major problem but you can almost buy a new motor for what most repair shops will charge you to fix it. I would looking around at some of the small engine repair shops for a used engine. Sorry no good news but it is not an uncommon problem. I have two 10 HP that I am going to have to put rings in myself.
Good luck!
Col. Dana Gillespie

Oct 12, 2014 | Garden

1 Answer

I'm looking at buying a 99 polaris xplorer 300 the

That should be a fairly simple job, if the cylinder wall is not scored. Pulling the head and cylinder is fairly easy and getting the piston off the rod is not hard either. You may want to go with an oversized piston and rings and then have the cylinder machined for that size piston.

Aug 19, 2013 | Motorcycles

1 Answer

Replaced rings and honed the cylinder but its scored up again and the rings were stuck in the piston and were hard to remove

Your description indicates when the engine started the piston wasn't receiving any lubrication or maybe the rings were too tight or both and the engine suffered pre-seizure.

It is well to observe the basics with these sort of things and take nothing for granted. Prior to fitting piston rings it is important to check the ring end gaps. Most popular repair manuals will have diagrams about this and the recommended gap for your engine which is likely to be something like 4 - 6 thou per inch of bore. Quite often the piston ring ends must be filed a little...

In addition it is important to ensure the piston ring grooves have been thoroughly cleaned of carbon and the rings fit well with a side play of 0.0015 inch. A little more is permissible and perhaps as much as 4 thou for the top ring but more than that and the piston should be replaced.

Apr 07, 2017 | Motorcycles

1 Answer

My 16 year old son ran straight gas in blower for approxiamately 5 min. until unit shut off. Piston has not seized up in cyl. head. It's trying to run but won't. Without tearing it down, what parts...

Yep , Sounds like the rings have probable seized to the piston. It will probably be on the exhaust side so you may be able to take off the muffler and look inside the cylinder there to see if there are any score marks. Good luck.

Jan 05, 2011 | Echo Gas Blower 162 MPH 450 CFM Blower...

1 Answer

Piston seizure in Husky 359 chain saw-how to remove old top end, evaluate damage and install new piston and ring or all new top end.

Probably going to be a paired piston&cylinder
you will need to replace both.. remove your muffler and see scorched(black streaks) piston, fused rings. Remove air filter and carb to see scored cylinder wall(on hot side)

Aug 23, 2010 | Husqvarna Chain Saw 20" Bar

1 Answer

My chainsaw was not working so I took it to a mechanic. He said someone ran it on pure gasoline and ruined the engine. Is there anything I can do?

Remove the muffler and check the condition of the piston skirt and what you can see of the inner cylinder wall. If badly scored, then the mechanic gave you good information. If shiny and smooth, then there is hope. Many engines will run fairly well with minor scoring but can be hard starting. If it has indeed been run without oil in the fuel, then considering the cost of parts plus labor, you can buy a new saw that solves all of your problems plus you get a warranty to cover any early problems. If the old engine seems to have fairly good compression, get back to us for further hints. Good luck!

Jun 23, 2010 | Garden

2 Answers

I'm unable to start the engine.It won't even kick over.

Most likely you have low compression caused by stuck piston ring or a scored piston and cylinder. This unit was made by Poulan and
they have had an epidemic of this problem. The solution is to tear the unit down and put in new piston rings. Before you install the
new rings you need to get a sheet of glass and some 600 grit wet dry sand paper. Sand each ring down about .002 to .003 and reinstall. This should solve your problem as long as you have good fire and the piston and cylinder is not scored.

Your cylinder could also just be worn out. This blower has a fairly short engine life.

Sep 21, 2009 | Poulan Featherlite Gas Blower, with Low...

2 Answers

2002 honda CR125R

sounds like you might have broken a piston ring. Sometimes a small piece will break-off and cause the loss of compression and if you look down the cylinder you wont see it. But it's enough to cause a problem.

Apr 30, 2009 | 2002 Honda CR 125 R

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