Engine issues need some help

niz55

Well-Known Member
Messages
800
Engine is a 34cc esp ported head with OBR case.
Almost 2 gallons on it. Lately couldn't get it to run correctly no matter how I tuned the carb. Engine bogs really bad under full throttle and dies. I took out the motor to see what was the problem and found out the crank has side to side movent. The piston also moves side to side as seen in the video.

Could it be the OBR case?


 

spents

Uncle Fester👻
PLUS member
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1,687
Location
oop north
crank should have a small amount of end play niz, hard to tell from your vid if its to much though,
piston i'd say maybe bad wrist pin or wrist pin bearing if the piston movement is excessive,
give the engine a strip and a proper close inspection for wear etc (y) ,
oh, and not sure about newer OBR cases, but my plder 2016 OBR reed case uses no gasket, just a smear of sealer between the cases,
if thats the case with your cases then maybe a gaskets been fitted and thats causing the cranks excessive end play,
double check if a gaskets needed for your cases and then check if its right if that makes sense,
 

Clubin

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Build Thread Contributor
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1,622
Location
Manitoba
These thoughts are all outside the box.

Varify the pulse port is clear. Easy to try another carb. I’ve had crappy ignition coils too, good when cold but not when warmed up. If you have a spare coil try one.
 

TODD

Well-Known Member
Messages
258
if using a stock isolator block on the carb? Pull it off and check it for flat. Even brand new never been ran engines I have seen warped iso blocks on the engines.
 

niz55

Well-Known Member
Messages
800
I have already changed out the carb 3 times and same issue.

Anyways I took the motor apart and the obr case seems to be little wide and not within spec.

Measured the axle play and is 1.87mm. specs supposed to me less than 0.5mm.

Just going to replace the crank case with a zenoah. Before I order the parts here some pictures. Let me know if the cylinder is still good shape. The piston looks great so as the crank.

Lots of play



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Clubin

Well-Known Member
Build Thread Contributor
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Location
Manitoba
Ho do the crank case bearings feel. Specifically the flywheel side. Are the bearings tight in the case?

Cylinder and piston-look perfect To me too. I’d re ring it.

As for that play! That’s lots. Something isn’t rite.

Case is a good start. Make sure it’s clearanced for a 2mm stroked crank.
 

niz55

Well-Known Member
Messages
800
Bearings look and feel great on both side.

Ddm has a new take off one modded for the 2+ for $89. Pretty good deal as I don't have any stock crank cases.
 

Rep732

The alchemist ☠️
Community Leader
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Any plans for the obr case? Id be interested in it just to see why its got so much slop. Also any pics of the inside of the case halves? Curious to see the bearings nizz.
 
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