My brothers computer is down so I am helping him out. He has his Raptor in the shop for the infamous tranny problem and while it is in he is thinking about putting in a Hich comp piston and a cam. The shop said they would do it for an aditional hour in labor. Good deal. They are offering a low-mid range power cam and a 10:1 piston. Parts cost is $500.00. Is this a good deal? I also wonder if 10:1 is really worth it? I know in the Bombs talk is normally 11:1 to 12.5:1. He wants to run pump gas if possible. What do you Yamaha guys recommend? Thanks a mil and I have to let them know by tomorrow.

 

fst has it. runs perfect on 93.

 

You may want to consult Trinity for the parts. If my memory serves me correct, You can get a JE 11:1 piston ($250), a cam ($160 + your old cam), that's $410. Have it bored for to accept a 102mm piston and now you have a 686.

Where you will really see the performance change, is having the head ported. Trinity has this down to a science, as they have been modifying the Rap for quite some time now.

A word of caution, due to the tranny failure your brother has just experienced:

First, make sure the shop looks at the oil pump gear on the back of the clutch assembly. It is the the smallest gear on the assembly and it's also the only "nylon" gear. Because it is nylon, when something fails in the Rap motor, typically the gear will be damaged, but many shops for some reason fail to look at this closely. I would bet that atleast half of the Rap owners who have had a tranny fail, have a damaged oil pump gear that was left in the bike after replacing the tranny. Just one of those small items that gets over looked and could cause some real damage later on!

Second, if the trans locked up on him or jolted his Rap to a hard fail, have the rod looked at. I had my rod fail about 6 months after my tranny failure and one thought for the rod fail was the sudden inmpact of the tranny failure. Your brother might even consider using a Carillo rod ($250) if he is thinking of modifying his Rap for more power.


Swy

 

Thanks Guys!! I think he is going to hold off for now. I think we might do it later this year in the down time for winter. I am going to talk to them about the Oil pump gear though. Thanks again!!