RODBOLT! Hole in Piston. '89 Suzuki DT55

[summers1996]

1989, suzuki dt55. While running on plane I suddenly lost power. The engine would run but at low speed. I pulled the (3) plugs and found the center plug was wet w/ oil and particles of something on it. Ran a wire into the plug hole and found a hole in the center piston. I know a lean condition can cause this. What are possible causes of a lean condition? I dont see any metal particles above or below the 1 and 3 piston and crank. If all checks out well, can I just rebuild the center piston, bearing and rod? Or am I asking for more trouble? Can an air leak in in the fuel pump, head gasket or crank seals cause a lean condition or is this carb related? I assume it has been rebuilt in the past, will the pistons be marked with new size? Any input would be greatly appreciated.

 

[rodbolt]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

sux bean U <br /> almost any thing that will alter the amount of fuel VS air in the cyl will cause a lean out.<br /> if the pistons have been changed the size will be marked, I happen to have a power head that I was rebuilding when I lost intrest in the project, new .05mm pistons and a rebuilt crank. I assembled the block a year ago and thats as far as it got.<br />I may sell it but I would reccomend a dissasembly and inspection cause dirt daubers may have bit it.<br />if your crank is not damaged you can do a one piston overhaul.

 

[summers1996]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

Thanks rodbolt, I will continue the tear down and inspect the crank. If it looks beat, I'll post again and get in contact with you about $ for your project. Can a air leak in the fuel pump or fuel line cause the lean-out?

 

[rodbolt]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

can that air leak alter the fuel/air mix in the crankcase ?

 

[summers1996]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

Yes, I believe it would. Thanks for all the info. Will be torn down this weekend and then to Brownspoint for the parts, thanks again.

 

[Ray Neudecker]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

Need to examine piston when you tear it down. Many times this is caused by gas which has been stored too long and lost its octane causing the detonation that burns the hole. Always go through the fuel system when rebuilding a motor.

 

[summers1996]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

Thanks Ray, what am I looking for in particular on the piston? I can see the lower piston looks fine, the middle piston has the hole (carbon and pitted) and the top piston is also carbonized and is a little bit pitted. I may replace all 3. I noticed when removing the fuel pump that one of the fuel line tubes (the metal ball and tube that bolts onto the pump)was easily movable. Could this be a cause of an air leak (may be a silly question). I bought this motor from an owner in Connecticut. They have to burn Gasohol up north. Could this cause a low octane condition or affect? Would an octane boost additive be recomended in the future or just stick w/ high octane fuel? I am using a manual but it can be a bit vague as to cause and affect.

 

[Ray Neudecker]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

We don't have the gasahol in this area, but your description of the damage would indicate that fuel quality could very well be a major cause. Any other problems in the fuel system would add to the initial problem and bring on the detonation earlier. I have seen a great increase in the fuel quality causing this in the last few years. Fresh gas seems to be the best solution. Going to a higher octane will give some insurance if the engine is not used on a regular basis.

 

[summers1996]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

Ray and Rodbolt, Thanks for all your input. Tore down the motor this weekend and it looks amazingly good. I ordered a new piston and rings for all 3. New oil seals and rebuild parts for the fuel pump. Would you recommend I hone the cylinders w/ a straight hone or the honeycomb/bee hive type?

 

[summers1996]

Re: RODBOLT! Hole in Piston. '89 Suzuki DT55

Thanks for all the help gentelmen. The motor is back together. Compression looks ok on all 3. Must have put the fuel pump together wrong, won't kick over and I have good spark. I'll get it fixed. Brown's Point is fantastic.