Group K?

[mxd253]

Hey does anyone have a 633cc (early 90's) super jet with one of the Group K mods? Id like to see some feed back on either the "Sleeper or the 96 Hammer" Their 701cc big bore sounds like a pretty interesting engine upgrade and from the little that I've read its a pretty affordable way to get max power from the 6M6 style engine.

 

[ATS_Aaron]

More affordable = buy some 701 pistons and a 633 sport port template. Port the cylinders and then get it bored to match the 701 pistons. Get the head milled or buy an aftermarket head. We did this to one about 3 years ago. Great running ski.

 

[mxd253]

where can I obtain a porting template? Great thing is I have access to boring maching and all the tools I would ever need to port and polish clyinders. This would eliminate the need to rely on Group K. Sweet!

 

[kevbo]

Find a 701 cylinder. They are about as good as a ported 650 cyl. If you want to spend the time to learn something new then cut your 650.

 

[Matt_E]

Be very careful using a 701 porting template on a 650 cylinder. You may very well break through the water jacket trying to widen the exhaust ports.

 

[smoofers]

If you send "TJLSuperjet" a message I'm sure he will tell you all about his motor (650). It was given the "hammer" kit by Harry at GroupK about 14 years ago. The motor runs like a bat out of hell, way stronger than some 701s I have ridden. The fact that it has gone 14 years without a rebuild is a testament to Harry's knowledge and skills.

 

[chriselmore_1]

I would go for it if tou do it yourself, but I would never put that much money in a 650 when a 61x conversion will cost less than a group k job.i will have lightly ported 61x cases intake mani reeds for sale soon for cheap.youd be alot better that route

 

[ATS_Aaron]

where can I obtain a porting template? Great thing is I have access to boring maching and all the tools I would ever need to port and polish clyinders. This would eliminate the need to rely on Group K. Sweet!

PM ATS_Scott. He has the 650 Porting templates.

Aaron

 

[jetski9010]

Like MattE said you gotta be careful porting the 650 motor with a 701 templete because you will break into the water jacket. I ported a 650 not to long ago and widen the exhaust to 66%-67% and rised the port about 1mm to match the cylinder better. This made the engine have great power but the biggest thing I ran into was it had lightswitch power really bad. The stock 650 ports are very undersized. If you open just the exhaust to what it can be to make good power the transfer are badly undersized and will create the lightswitch feel. If you have the know how and the tools to do the transfer work then I would say go ahead and do it. If you dont then like everyone else is saying go with 61X 701 cylinders.

 

[Tyler Zane]

so what do yall think the 701 to a 845? they use a 760 cylinder.... port and match everything