My frame looks like it's a little too small for my engine, but I really don't want to find a new bike. What should I do? Pic below.
Mounting issue
- Thread starter ballinchestr
- Start date
Hard to tell from that photo but it appears all you need to do is lower the engine in the frame. What are we missing?
Tom
Tom
The angle is wrong and there appears to be an extra part on the front mount. I think you want that part on the rear mount where it attaches to the seat tube.
Tom
Tom
I'm just using that part as a spacer, it doesn't fit either tube.
Is the engine's angle wrong? or just the mounts?
Theons right. I'ld do an offset intake and to bring it lower Put rear mount in bench vise and shave an eigth / quarter or so off. I've done this procedure to eliminate chain tensioners also. Look at the happy chains album in my profile for pics.
I'm not quite understanding here. What is the part you have attached to the front engine mount?
The engine needs to rotate clockwise as you look at your photo and sit lower in the frame. You might need a custom/aftermarket front mount but the rear mount should attach easily to the seat tube. That will give you approximately the right mounting angle.
If the frame tubing is too big for the engine mount saddles you can open them up a little with a grinder/file/sanding drum, but if the frame tubeing is too big you will have to fabricate both front and rear mounts...or look for another bike to motorize.
Can you provide a better photo of the rear mount where it touches the seat tube? That would help us offer more suggestions.
If you have spark plug interference with the frame the cylinder head can be rotated 180 degrees putting the plug facing forward. However, if the engine is mounted that high you'll have throttle cable issues. Also I think I'm seeing a water bottle holder screw head. That can be removed to give the front mount a place to rest.
Tom
The engine needs to rotate clockwise as you look at your photo and sit lower in the frame. You might need a custom/aftermarket front mount but the rear mount should attach easily to the seat tube. That will give you approximately the right mounting angle.
If the frame tubing is too big for the engine mount saddles you can open them up a little with a grinder/file/sanding drum, but if the frame tubeing is too big you will have to fabricate both front and rear mounts...or look for another bike to motorize.
Can you provide a better photo of the rear mount where it touches the seat tube? That would help us offer more suggestions.
If you have spark plug interference with the frame the cylinder head can be rotated 180 degrees putting the plug facing forward. However, if the engine is mounted that high you'll have throttle cable issues. Also I think I'm seeing a water bottle holder screw head. That can be removed to give the front mount a place to rest.
Tom
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I concur. The Seat Post should determine your angle. Take your time, think about this-with all of the above in mind.
Okay, I grinded down the rear saddle, and it looks like the engine will mount okay, the angle is defined by the seat tube now. Spark plug fits too.
Only problem is that the carb barely fits, and it has to be tilted 5-10 degrees to the left or right to let the cable through. Can it run in this position, or do I need an offset manifold?
Only problem is that the carb barely fits, and it has to be tilted 5-10 degrees to the left or right to let the cable through. Can it run in this position, or do I need an offset manifold?
Five to ten degrees shouldn't really give you any problems. Keep the angle as small as you can to get throttle cable clearance and you should be good.
What did you do on the front mount?
Tom
What did you do on the front mount?
Tom
Since the tubing is like 2.75, I just fabbed a mounting plate out of some steel sheets, and bolted it to the mounting saddle, sort of covering the U shape of the saddle. then I drilled holes for a U-bolt.
I ran my original Pig with the carb barely stuffed in like you describe. I ran it tilted for cable adjuster clearance for several months with no issues at all.
Later I ended up removing the adjuster altogether to get it straight and this worked fine as well. The carb slide does not allow enough air leakage to change the mixture so running it with no adjuster does not harm anything.
Later I ended up removing the adjuster altogether to get it straight and this worked fine as well. The carb slide does not allow enough air leakage to change the mixture so running it with no adjuster does not harm anything.
Okay thanks everyone. just one more thing. One of the stupid, cheapo engine bolts that holds the jug and cylinder head on snapped while I was tightening it...will threaded rods at home depot work, or is it some non standard thread?
"Snapped" where? The stud or the threads in the case?
Here is another case of over tightening. It is why I stress the use of a torque wrench when working on these little engines. The max torque for the cylinder studs/nuts is about 150 inch pounds. Anything over that and you're asking for trouble.
If the threads in the case are stripped you'll need to go the Heli-Coil route. If the stud broke there are replacements available from many sources. Home Depot won't have the right stuff.
Some engines have studs with fine thread on one end and course on the other. Some have the same threads at each end. Yours are probably 8mm and the threads might be 1 or 1.25 or both.
Also the chrome acorn nuts that come with the engine are notorious for bottoming out before they tighten against the cylinder head. We always recommend that they be replaced in favor of shouldered, or flanged hex nuts.
Tom
Here is another case of over tightening. It is why I stress the use of a torque wrench when working on these little engines. The max torque for the cylinder studs/nuts is about 150 inch pounds. Anything over that and you're asking for trouble.
If the threads in the case are stripped you'll need to go the Heli-Coil route. If the stud broke there are replacements available from many sources. Home Depot won't have the right stuff.
Some engines have studs with fine thread on one end and course on the other. Some have the same threads at each end. Yours are probably 8mm and the threads might be 1 or 1.25 or both.
Also the chrome acorn nuts that come with the engine are notorious for bottoming out before they tighten against the cylinder head. We always recommend that they be replaced in favor of shouldered, or flanged hex nuts.
Tom
It snapped at the stud, right below the nut. I think it's 6mm, I because I have the 49cc engine.
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If you have 6mm studs then the max torque will be in the 50 to 60 inch pound range. That isn't much and can easily result in breakage if you heavy hand them.
You'll need to remove the cylinder head and if there is enough stud to get vice grips on you should be able to turn it out. If not then you'll need to remove the complete cylinder to extract the broken stud.
Good luck. Let us know how you make out.
Tom
Only one of them snapped, and I removed it easily. I found studs sold by the same seller that I bought the bike from, so I'll order those asap
