two failures

deacon · #1 (**permalink**) 08-24-2008, 03:28 PM

I need to rethink my mount. I had a second engine fail at the cast alum case. The mtv 25 just started to crack. I'm not sure what I need to do to prevent this in the future. I for sure need to rethink it.

The engine's mount should be fine it might need to be stiffened up some. I might need to change the way the engine attaches as well. It's the vibration that kills it I think.

I am thinking a change in rigidity of the frame is needed but that the motor hinges on a separate frame. I need to work it out before the new engine arrives. I also need to work it out because I need a new engine for the mtb now lol.

I for sure am going to have a lot of spare parts around.

Jemma Hawtrey · #2 (**permalink**) 08-24-2008, 03:54 PM

Triple mount would solve that problem. Secure front rear mounts and fabricate something that supports the top of the engine. Means there is three mounts to take the stress, not just two.

Use the forward studs on the motor and a u strap connect to them and thence to the frame?.

deacon · #3 (**permalink**) 08-24-2008, 04:53 PM

The engine cooled down enough for me to check it out. I found that it was the mount that I forgot to put the tie bar on. The mount is actually built to the motor and I forgot to tie the top and bottom rails together at the rear. The road vibration twisted the mount because the brace was missing so all is not lost.

Of course the engine is ruined but I have more spare parts now. I guess the chainsaw bike will get a lot more use now. Actually I was giving thought to getting rid of the 25cc anyway. More power more power lol.

I do use a u strap on the front and tie it down, but with a spring. The gravity clutch requires that the engine move.

I think the chainsaw bike and the new full suspension will be enough for me, even if I sell the china bike.

deacon · #4 (**permalink**) 08-25-2008, 03:18 PM

Well the autopsy is complete on the mtb25 bike. The engine's housing broke in two places. Both were caused by careless assembly not poor design. one of the screws that goes directly into the engine's housing through the mount had slipped out of the mount. It seems someone (that would be me) left the flat washer off. For lack of the flat washer the bike was lost.

It didn't hurt that I also forgot to install a brace for the mount that I realized only after the bike had run several miles. All in all it was lessons well learned on a not too expensive engine.

Im not sure what I will do with the mtb now. I tried the 17cc gifted engine but the load kills it. The engine runs fine when not under a load but put a load on it and it dies.

I expect the engine to become an organ donar. As for the bike, it has some parts I can use as well. Being a mtb the rear wheel and the crank set are of no use to me, but the tires and controls should be useful someday.