The damage report to the JM150 is growing. Hopefully, it will be fixed once and for all tomorrow.

Here is the background:

Bought the JM150 about a 18 months ago and my son has ridden it a fair amount and fairly hard. I've kept a watchful eye over it and kept all the bolts tight, chain adjusted, oil changed, etc.

This summer I started noticing problems keeping the chain adjusted. Late summer I finally noticed the swing arm bushings were shot, causing a lot of slop in the swing arm. Ah... that is why the chain adjustment was so whacky; never could get it just right. Replaced both bushings and the chain adjusted up better.

Last week, after a few months of no riding, I noticed a wear spot on the swing arm where a bolt on the back end of the engine was hitting. I thought oh... it was the slop in the swing arm that allowed the engine and swing arm to hit.

Upon further investigation I noticed that there was a crack in the welding on the upper rear engine mount. I took it over the the local mechanic and he noticed another crack on the lower frame and said the engine had to come out to get enough access to prep and weld it properly. While removing the engine, I discovered the lower rear mount bolt was missing. Now that really threw me as that is a long bolt and very hard to "fall out".

Now I am trying to together all the factors that created this mess and it is not clear what the sequence of events were that triggered off so many repairs. I am going to assume the lower rear engine mount bolt was never installed and that allowed the engine to have some slack which then caused added jolting and jerking between the engine and rear end. This caused the swing arm to go under unusual stress that caused the bushings to fail. That allowed the swing arm and engine to bang against each other causing the wear spot on the swing arm from the bolt on the engine. That banging caused the upper rear engine mount to sustain unusual forces that caused it to crack.

At least that is my version of how so many parts could be affected. I am certain they are all related. I just wish I had noticed the missing bolt earlier and also discovered the source of the problem earlier.

Obviously, all you '07 JM 150 owners will want to take a quick peek to ensure all engine mounts are secure and the swing arm is rock solid to avoid the problems I have suffered.

Still, I am overall quite happy with the purchase, particularly since I always anticipated more maintenance and service work over the long haul. It was a pay up front or pay as you go plan. Could not pay up front and the pay as you go as been relatively pain free given the outings and hours enjoying the outdoors on the ATVs.

Here are a few pics to see the details. Forgive the lousy quality, blame the camera in the cell.

Upper engine mount crackMount is cracked on both sides as well as crack on top.

Lower engine mount crackThe spacer tube was spot welded but those broke but the tube remained in place even without the bolt.

Lower frame crackThis crack runs on both side of the tube. The hole/spot on the top seems like a place where the weld may have burned through the tube at the factory. The crack does not appear underneath.

Swing arm contactThis wear spot is on the swing arm where a rear engine bolt put the groove in the tube. Engine seems fine.

 

Repairs done! What an ordeal.

Day 1 - take bike to shop to weld cracked top rear engine mount. Mechanic notices that frame has a small crack and also the lower rear mount needs spacer to be tacked again. Engine needs to come out.

Day 2 - Engine out and back to shop.

Day 3 - pick up bike. Nice welding, frame is good again. Sand, prime, paint.

Day 4 - Engine back in but lots of problems. Replaced the missing engine mount bolt but had to go to three places to find a m8 x 150. Get home then find out it won't it as there is an alignment problem with the rear holes not quite lining up. Back to hardware store to get a 1/4" x 5", smaller than the m8. It fits. One of the exhaust studs came out and the nut sheared off while trying to remove it. Back to the hardware store to find stud; had to use a hex bolt and hack off head. Discovered the gaskets on the exhaust were shot. In the car AGAIN. This time to the cycle shop. No luck finding right gasket so off to Kragen and Pep Boys looking for gasket making materials. Finally, all back together and running great!

The more I spent working on this the more I think what happened is the rear engine mounts were not spaced properly from the factory and when one of the bolts would not fit they just didn't bother correcting it. So, from day one the bike never properly supported the engine and all the symptoms and problems I experienced resulted from this missing engine mount bolt.

Moral of story - take a look at all your engine mounts and make darn sure they are all secure.

 

now you feel my pain

 

I will have to inspect mine, but not now it's snowing and to darn cold out!

 

The 150 runs tighter and better than in all the time we have run it. The engine is rock solid and does not move a bit, not even any vibration to speak of. When getting on the gas and off the whole drivechain is totally tight and zero slop. The chain adjusts like it is supposed to and does not show any unusual looseness. Trilled to have it working so well, too bad it too nearly 18 months to figure out what the real problem was/