125 Mod motor mount

[GrandpaRacer]

We had our first 125 Mod race on the west coast at the Nationals last week. Sadly there were only 3 of us since others just were not ready. Our boat did not make the start due to engine mount bolts vibrating out. No, we did not loose the power head. At the time I could not remember if I used Locktite. Well I did and the 4 6mm bolts still worked loose. Have any of you guys switched to 8mm fine thread bolts? The normal mounts for GoKarts are 8 mm and I think that may be a better size to resist working loose. I did not use a lock washer. Any advice?

[Dan M]

GrandpaRacer,

When we were running 125 Pro, we had a lot of issues with bad vibration and loose bolts. We changed from bolts to studs wherever possible. This gives the advantage of being able to use red (permanent) Loctite on the studs in to the block, and nyloc nuts with lockwashers to secure the powerhead.

Removing the studs from the powerhead takes a little heat, but does not need to be done often.

Dan

[GrandpaRacer]

I had used blue Locktite, will switch to red and will go to studs. One of the 6 mm cap screws I used actually broke the head off!

[modhydro]

I didn't trust just the 4 6mm bolts so made my towers such that there is a 3/8" plate that picks up on the 8mm kart mount bolts that are now on the front of the engine (bottom when on a kart.) Here are a couple of photos. I'd recommend figuring out something similar for your mounts. We haven't had any issues with anything loosening up on ours and Cliff Johnsons with this method.

[GrandpaRacer]

Cliff was telling me about this trick at the Nationals. Just picking up two of those 8mm mounts will help for sure. Now I see how you did it, thank you.

[GrandpaRacer]

Do you think there is enough material around the 6mm holes for me to safely put 8 mm studs there?

[GrandpaRacer]

ModHydro, I decided to make a mount like yours for my OMC tower. In addition I changed two of the 6mm bolts to 8mm, the two nearest the piston where there was more metal in the base to support 8mm bolts. Unless I make a whole new adaptor plat I can not use studs, so with red Locktite I am hoping this will be the answer. Eventually I will switch to a cool short tower but want to stay with the OMC while we determine which sized boat works best.

[bmitch1]

FYI - We used 5 x 6mm cap head bolts for our OMC-based motor. In addition to the primary 4 around the drive shaft we have the 5th on the front port-side hole. So far we have not had problems. I removed the powerhead before nationals to check over equipment and they had not loosened from when it was built this spring. That's 3 race weekends of hydro and runabout plus testing days...fwiw

[GrandpaRacer]

Sorry we could not make it out on Saturday but thanks for your help and advice at the Nationals. It was great meetng you and hopefully we can race together another time!
John Adams