Winter Project

[Fa-bam]

I'm moving this here from the "technical forum" because of a suggestion.

I've got a '77 GS750 with 30k original miles on it. The bike was in storage for a long time before I bought it for 200 bucks. This winter, I'm considering rebuilding the top half of the motor and going to a big bore kit.

From my understanding, the bottom ends of these motors are very strong, therefore I'm considering not rebuilding it.

I have a lot of general mechanical knowledge as well as over 6 years experience working on cars and about a years experience building drag car chassis, so I feel competent enough to do this project with a little informational help from you guys.

I'm looking to make the bike a bit faster but keep/improve dependability and not build too much power for the current wheel/tire/transmission combo to handle. Also, I would prefer to not get too far into modifying the motor/transmission because I'd like to keep the project in the 2k range.

I was turned onto a Wiseco 844 Big Bore kit and Webcams for cams/springs/retainers. Are there any other sources I can go to for parts and ideas?

Any ideas on combinations from you guys?

Finally, is there any technical information I should know (ie... how to remove/install the cylinders, what kind of machine shops will bore the cylinders, etc...)


Thanks

Erik

[49er]

I'm looking to make the bike a bit faster but keep/improve dependability and not build too much power for the current wheel/tire/transmission combo to handle. Also, I would prefer to not get too far into modifying the motor/transmission because I'd like to keep the project in the 2k range.

I was turned onto a Wiseco 844 Big Bore kit and Webcams for cams/springs/retainers. Are there any other sources I can go to for parts and ideas?



If you are looking for good improvement in torque, don't change your cams or carbs.
Source a set of 850 barrels and head. These barrels will fit on your 750 crankcase after minor relieving work around the stud area. You should be able to pick up these cheaply on Ebay.
With the 850 barrels, you can bore out safely to 71mm bringing you to 894cc.
I had a set of 71mm pistons made by JE pistons at 10.5-1 for my 850. They work great. If you are interested in going down this path, PM me for more information.
Incidently, your stock 750 barrels will only have 1mm wall thickness left on the sleeves if you fit that 844 Wiseco kit. IMO, that is getting too thin for good heat dissipation and wall stability. Without adequate wall stability, your engine will suffer from ring flutter, reducing it's performance.