Sam you would need the case machined and the cyl. bored to take a larger sleeve.

 

which ever way you go you need to replace the rod.
go ahead and spend the bucks and get the 727 or 740 it will save you money in the long run. because sooner or later you will upgrade to the 727 if you get anything smaller. so save money and get it all done now and get the best when doing it.

 

Yamaha660R... I've been around just been kinda bussy trying to find a way to deal with my drag race withdraws! I was playing Need for speed underground last night and was on one of the drag races and started to shake! I neeeeed to race!!!!!! LOL

I have to agree with daboss... Get the 727 now the case work will be done and you will have a FAST bike! If you go with the 686 down the road you are going to want the 727. Thats my .02 cents there are probably alot of 686 guys out there that don't agree.

 

About time you start checking these forums again. I thought you got lost in your garage or something. Before long I'm going to start building on my Raptor's motor. Probaly not a 727 but alittle higher compression piston, and a stage 1 or 2 cam. I still haven't decided. But I did finally get to race a YFZ. The results were good.

 

Glad to hear you are holding your own with the YFZ's!

We will have to meet at the track next season and make a few runs!

 

Sixsixt, 14 mins, or whom ever else is in the know. If a guy was wanting the 686, but are still trying to pay off the ride so he doesn't have $1500-$2000 right now, what are the steps that he can do to get aimed in that direction? New cam? Higher comp piston? port polish? Or should I wait and go with the whole kit?

Also, 14 mins, How do I go about getting a craycraft kit? Do I send in the motor, or do is the kit sent to me and I have someone do the machine work?

 

You can do a Stage 1 cam without pulling the head, the Stage 2 cam requires new valve springs so you have to pull the head or figure out a way to keep the valves from falling into the motor while changing springs. For a high compression piston, you've got to pull the head and bore the jug, that's the time to have the port and coating work done. When I upgraded to the Craycraft Signature motor (minus the SS valves), I shipped the head and jug to Craycraft and they did all the machine work (bored the jug, fitted the rings, port, polish, high temp and friction coatings, valve job, new valve springs). Craycraft sent back my jug and head along with the Stage 2 cam, piston, rings, carb jets, and gaskets. If you are not comfortable doing the engine work, you can ship the whole engine and they will send it back fully assembled. I would not let a local machine shop do the work for the little bit of shipping cost to have Craycraft do it.

 

Amen! Bartlett.

 

Don't forget the carb boots. They match those to the intake as part of their port job.
I would do the engine all at once. I don't know what you have now but until you do the engine I would do a pipe, carb mod and eliminate the air box unless you ride in real wet and muddy stuff.

 

I agree with replacing the rod (especially if the cases are split!)

What is the 740? Stroke or Bore? What bore? Are the piston and sleeve standard items I can get?