Noticed my Engine Mount bolt broken off, couple questions

XS650D

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I have been noticing a vibration and noise from front of bike for a while now that I just couldn't
figure out till today by accident.Was out looking over bike carefully for anything that jumps out
as a potential problem and noticed that the engine mount bolt directly under motor had the nut missing
and head of the bolt sheered clean off and the bolt or whats left of it had worked its way out were it was rubbing on the
inside edge of the manifold pipe on the clutch side. Luckly the pipe was in the way or it would have come completely out. It was no longer attached to the frame on the chain side.Either someone over tightened it when the motor came out with the previous owner or vibration caused it but I doubt it. That sucker is like 11" long, hopefully the hardware store will have.
Could that have caused any issues.I have noticed that I couldn't get my chain to stay tight regardless of how tight I made the axle nut, could that be the culprit. What other issues could that potentially have created .
Dam you gotta luv old bikes, contant attention but still worth it!
 
Yamaha does not carry this bolt any more.Does anyone know what the metric size or thickness of this Engine
mount bolt. Is it the same thickness as the 2 longer bolts at the front of the engine that hold the front mount to the frame.
 
Yamaha does not carry this bolt any more.Does anyone know what the metric size or thickness of this Engine
mount bolt. Is it the same thickness as the 2 longer bolts at the front of the engine that hold the front mount to the frame.
get the yamaha part number then search here on decoding part numbers. The size is encoded in the part number. Best bet might be ebay or the boneyard
 
Thx Looked thru a ton of threads and came up with M10x1x265. I have the Yamaha parts book but
its for a 1976 . The number is #90109-10388 Not sure how to read that.The 10M sounds correct but not sure
on the rest of the number.
 
Thx,callin the hardware store in morning.Any idea if this bolt not connected to the frame on the chain side would effect chain tension?
 
Well you aren't going to find that bolt in the hardware so a 3/8" x10" lag bolt or a piece of 3/8 all thread with nuts and lock washers will let you snug it up "for now".
No this bolt being MIA isn't the chain issue, how old, worn, are the chain, sprockets? Have the wheel bearings been replaced? (missing sleeve) Check to be sure your rear wheel, axle are assembled / installed correctly. More than one has found errors in rear wheel assembly. That can get ugly fast.
 
^Good catch :yikes:

The part #90109-10388. I think the 901 beginning means it won't decode right. It sounds like you found the right size though. Ebay or junkyard and you won't need that info anyway. Call a few car junkyards or motorcycle mechanic and ask where the nearest motorcycle junkyard is. Put a want ad for it in the classifieds here too.
 
Contact mistermonkeyclaw through e-bay. He has several misc. bolt packages listed several which have the longer motor mount bolts.
 
You can't get the size of every nut or screw from the part numbers, only the normal or standard ones. Obviously, this one is special. With this bike's vibration level, it's not uncommon for engine mounting bolts to come loose or sometimes even break. Mine had that same bolt replaced when I got it. It wasn't a correct replacement, just something someone found that fit, but included with the bike was a brand new replacement from Yamaha. That was many years ago and I guess that bolt was still available back then.

Going over the rest of the engine mounting bolts when I installed the new replacement, I found not just a few, but ALL loose. My best guess is it's sort of a cascading effect. One motor bolt comes loose or breaks and that puts increased strain on the remaining ones. You should make it a habit to check all the engine bolts occasionally.
 
Engine mount bolts can cause a major problem when they come loose... I had one come loose on me one time and it slid out under the brake peddle and stopped the back brake from going down..... luckily I didn't have a major problem as I wasn't in town just on a country road
however that corner was harry ! LOL ... I pulled the bolt and put it back in from the other direction even though I had to take half the bike apart to do it.... ...there is a reason they say insert the bolt from the left side ...GRIN !
I think that was on my 305 honda many life times ago ! but I remember it well !
....
Bob........
 
Had to order a new Grade #8 bolt 3/8".Whats the torque spec on that bolt, will use a Nylon lock nut!
 
I advise you add a regular split ring lock washer as well. I have on most all my motor mount bolts. The factory lock nuts don't hold as well after they've been on and off a few times. As far as torque values go, this is another area where Yamaha changed their mind several times during the production run. Their last change to that bottom bolt near doubled it's value, from 36 up to 65 pounds. I won't use that, I think it's too much. I follow the '77 manual specs for pretty much the whole bike now. I like them because they are given as ranges instead of just one single number .....

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Why order a 3/8" bolt when you could order a 300 mm. long piece of 10x1.0 mm. threaded rod from McMaster-Carr, cut it to length, and use nyloc nuts on both ends?
 
A 3/8 bolt is stronger has a larger shank than the all thread, and it won't act like a lathe on the aluminum casting like all thread will? griz shipping from McMC to canadia ain't cheap either. but a factory bolt is still the best answer, cause that stock 3/8" bolt will have more threads than is ideal and is a touch undersize of 10mm.
 
If you have to order, why order a 3/8 when you can order a 10mm?
 
I concur Ggary, Its a bolt Grizid,not a great deal of cost, why go thru all that!
Wanted to get fine thread but only available in Grade 5. Also had to get coarse thread
but wanted fine thread (only available to 9.5" length.Thx for the Torque specs 5T, great info.
 
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