Rear mount studs broke, any good fix???

danlandberg

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Apr 25, 2009
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This is the third time the rear mount studs have sheared off at the block (case halves). :sick: The second engine I used 8.8 grade bolts, worked for 25-30 miles. Then failed again! I removed all studs from both engines, and replaced the studs on the engine I;m running with stock studs, broke again in 10 miles. I'm thinking of shuffle pins, or 8x1.25 studs. One other thought is to add a cold role aluminum plate under the mount spacer (between spacer & case) And adding two more mount bolts into block (case). :unsure: Will have to file the mount spacer (flat end) to accept the plate so I can keep the distance between the engine and seat tube the same. Any one have a sure fire fix for this problem?? :confused: ('' NEED INPUT'').........Dan
 


Al.Fisherman

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This is the third time the rear mount studs have sheared off at the block (case halves). :sick: The second engine I used 8.8 grade bolts, worked for 25-30 miles. Then failed again! I removed all studs from both engines, and replaced the studs on the engine I;m running with stock studs, broke again in 10 miles. I'm thinking of shuffle pins, or 8x1.25 studs. One other thought is to add a cold role aluminum plate under the mount spacer (between spacer & case) And adding two more mount bolts into block (case). :unsure: Will have to file the mount spacer (flat end) to accept the plate so I can keep the distance between the engine and seat tube the same. Any one have a sure fire fix for this problem?? :confused: ('' NEED INPUT'').........Dan
Dan, there are only a few reasons I can think of that the studs for the engine mount will break, other then a accident.
1. Engine not installed on frame correctly.
2. Torque not correct.
3. Engine twisting on the frame.

I have a solution for all three...

1. Was your engine mounted correctly, the mounts (both front and rear)) were flush with the frame? No binding what so ever. Perfect angle is 75 degrees, between tubes.
2. What torque were they torqued to? I use 50 inch pounds
3. Does you engine twist on the frame, to the left?

I don't think that 8mm would be a good idea, due to the thickness of the mount base.
 

danlandberg

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I agree that 8x1.25 is a little large in diameter. The left case half (drive sprocket side) does not have much material to work with. The engine is mounted as close as you can get to a "happy medium". These MICARGI bikes are junk! :poop: Much less put an engine on them. Now you have double trouble! :sick: The front mount is an adapter mount for large down tubes. I had to go with the billet intake & slant head To get the engine to fit. Don't know how much the engine twists. I do have a SBP x chamber, that does give me more torque & hp! I don't know if the mount angles differ between engines. RAW, GRUBEE, and Flying Horse. All I know is I have spent more on asprin than parts!!! I'm going to do a second set of mount screws. I will see if it works:whistle:
 

Al.Fisherman

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Dan, stay with the 6mm studs, going any larger even to 1/4" might be asking for trouble you can't fix. Since the stud broke and not the case you are lucky. I've said it before and I'll say it again, mount the engine to the frame, and not the frame to the engine. Start with mounting the rear mount to where you need it to be mounted. Then work on the front mount (I don't feel that the adapter mounts that are mass produced are one size fits all, although they are good for most applications)..the clamp is a standard muffler clamp, followed by the engine brace (4 picture in second link) I designed. Use double nuts, nylon locking nuts or both. NO washers between the nuts. I'm sure that these steps are why I haven't broken a mount. haven't broken a stud, and haven't had to tighten the mounts since installed. With the mount standoff (pictures in first link) you can attain the proper torque on the mounts. I lock tite all studs. I use red but most use blue. If red is used and stud needs to be removed heat will be needed. Having the equipment is no issue for me. And you already upgraded Grade and stay with grade 5 (metric 8.8).

http://www.motoredbikes.com/showthread.php?t=27147

http://www.motoredbikes.com/album.php?albumid=1018
Keep in mind the measurements here are for Chinese HT's
 

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Al.Fisherman

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Don't forget the muffler strap.
Correct and I'd recommend that the muffler be secured to the engine and not the frame, this way if there is movement with the engine on the frame there won't be additional stress on the exhaust studs. Both will move as 1 unit together.
 

danlandberg

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Apr 25, 2009
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There is no place to mount the exhaust to the engine! :sick: (SBP x chamber) I am trying to mod the rear mount for added strength. :unsure: :unsure: I'll post some pics tomorrow or the next day when I get done! :whistle: Hope it works! :cry:
 

danlandberg

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Apr 25, 2009
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rear mount repair

Hope this works! I drilled and tapped 2 more holes in the case halves to accept 2, 6 X 1.0 hardened button head Allen screws, inboard the stock mount studs, (just above center line), to hold a piece of cold role aluminum between the mount spacer and engine. :unsure: This might work. :rolleyes: If not, :unsure: I'm going to use 2, 5mm x 20mm role pins inboard the mount studs. (one above and one below center line of stock mount studs). If both methods fail, that will be strike 3 & your OUT! I'll find a frame that works, and cut this one up to make usable tools, (Forks for truing wheels, tail section for rear wheel truing, V section for engine add ons). I'll make stands out of every thing I can! That's all these MICARGI bikes are good for! SCRAP :poop: :sick: If anyone has bought a MICARGI DIY kit from B.B. I AM sorry I did not do it first :geek: So I could warn you that they are :poop:
 

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