Straight Cut Gears

[Anonymous]

I want to junk the helical gears on my crank and clutch on my GS1000 2V and fit a set of straight cuts. Am I correct in thinking that I can use the gears from a 2V GS750 (or are they helical?) or should I go the aftermarket route?

[Anonymous]

Is the bottom part of the engine similar to the GS1100 16v?
If so, why do you want to change? Is it modified a lot? On the GS1100 you can go to about 150-160 RWHP(rear wheel hp) without straight cut.

[Anonymous]

Yes, the bottom end is very similar to the GS1100 16v.

This engine will be (at least) 1238cc with lots of mods. and will eventually use lots of gas (and produce lots more than 150hp!!!)

[Dink]

Unless you are going to a car tyre type drag setup the 750 gears are a poor compromise, I suggest aftermarket.
Dink

[saaz]

If you are going straight cut go straight to aftermarket. No use skimping on the basics if you want that sort of power Crank rebuilding and clutch mods done properly will cost, so use the best bits as they are a small part of the cost

[massakins]

Yoshiman, I've built a couple of motors with straight cut gears and offer the following opinions.

Do you need it? It's a matter of load and cycles. How hard will the clutch hub be loaded?, (considers total HP, overall weight, rear tire type, type of HP (nitrous HP and carbed HP much more abrupt than turbo'd HP), clutch setup, riding style (street with roll on or dragstrip with throwing away the lever), 2 step or not, etc.) How many times will it be loaded this hard?, (considers number of passes every weekend at drags, or infrequent visits, etc.)

But if you do decide to do the conversion, some learnings: Two ratios are available, the gears from a GS750 2v (Option A: 99t on clutch hub and 46t on crank gear) or aftermarket gears with the same ratio as existing (Option B: 87t on clutch hub and 49t on crank gear).

Option A: I've bought these from boneyards in complete motors for $75. Had to disassemble and throw away most of the pieces (not much demand for resale) but kept the buckets, shims, hardware, primary drive gears and oil pump gears. Required disassembling the donor crank and clutch hub as well. Once the gears are free they can be installed on your crank and clutch the same way regardless of the ratio. However, the larger clutch hub gear requires clearancing the stock cases in two areas; I did this on a milling machine and had a plate welded on top to cover the hole but have been told its possible to do it without the hole (?). Second, you must use the high volume oil pump gears (38t clutch, 29t pump) to restore your oil flow. If already using these gears you may be able to get a different set from MRE (41t clutch, 27t pump plus clearance cases) to compensate accordingly. Third, you must compensate on your final drive for the different ratio; I found 1 additional tooth on the countershaft was about enough. Lastly, if you use a lockup or slider clutch you will now have to start from the beginning on your tuneup because of the different RPM range of the new gears. Bottom line, if $$$ are tight and time/skills are abundant, it worked for me several times.

Option B: Use the aftermarket gears of the same ratio. These used to be available for about $275-300 per set. Installation on the clutch and crankshaft is identical but no changes are needed to the cases, oil pump gears, final gearing or clutch tuneups. For the majority of folks this is the way to go. It's how I'll do it in the future.

When I began converting mine Option A was the only option. Since then things have changed. Another consideration is to retrofit GS1100 clutch hub to allow using these plates, especially if racing. GS1000 plates are getting harder and harder to find, especially affordable ones. I've had great luck with APE fibers ($90-100 per set), but OEM steels are still pricey. Have fun!

[nastyjones]

My gs 1000 is now about 160+ h.p. We run stock gears w/never any trouble. The bike is dragraced regularly and has been for the last 4 yrs. Any questions pm me.

Paul