GS 1000 straight cut Primary Gears

[John Kat]

I have the opportunity of buying some primary straight cut gears complete with a welded crankshaft
I believe these gears are manufactured by Novaracing in the UK: http://www.novaracing.co.uk/ProductS...maryGears.html
Has anyone any experience fitting these gears in the GS 1000 crankcase?
The question is prompted by the current owner who indicated that some material must be removed from the crankcase in order for the gears to fit

[rapidray]

There are only 2 ratios available in straight cut gears. The 1100 ratio uses an 87 tooth clutch hub gear while the 750 ratio uses a 99 tooth clutch hub gear. There would be no need to remove any material with the 1100 ratio stuff but the 750 ratio WILL REQUIRE material removal to clear the cases. The 1100 ratio is easier to deal with as it is a bolt in. The 750 ratio started to get popular because, in HIGH hp applications the clutch tuning window gets very narrow with the 1100 ratio. The 750 ratio slows the clutch basket down to give a bigger "tuning window". Another benefit with the 750 ratio is 6-8 teeth less required on the rear sprocket, less chain & therefore less weight for the engine to spin. I hope this helps explain the differences. Ray.

[cbxchris]

Ray, I assume the 1100 solid type basket is used in the 1000. If my memory is correct the stock 1000 basket was a skeleton type basket prone to break.

That right?

[posplayr]

Nice clear answer Ray.

[mrbridgeport]

Ray this 1100 ratio and 750 ratio straight cut gears. These are basically for drag bike applications not road race applications?

[trippivot]

very little material is removed with the 1100 ratio light clean up.

st cut gears are an excellent modification if you are going to make medium-big power - but with a 1000 you have other limiting factors - so it is money wasted in the long run.

[John Kat]

very little material is removed with the 1100 ratio light clean up.

st cut gears are an excellent modification if you are going to make medium-big power - but with a 1000 you have other limiting factors - so it is money wasted in the long run.

The guy from whom I'm buying this kit races sidecars.
This could explain why he chose this gear ratio?
The reason he's not going to use it anymore is that his competitors are leaving him standing with their GS 1100 16 valve engines.
My goal is to get a top 8 valve engine with GS 1100 "D ported" head and 73 mm pistons.
One day, I'll get an XR 69 chassis to complement the setup
PS: where do you need to remove the material from the cases?
Any pictures available?

[rapidray]

Most likely the reason he used 750 ratio gears is that the 1100 straight cut gears are aftermarket & not cheap. The 750 ratio gears come from stock 8 valve 750s & are easy to get cheap! Ray.

[John Kat]

Most likely the reason he used 750 ratio gears is that the 1100 straight cut gears are aftermarket & not cheap. The 750 ratio gears come from stock 8 valve 750s & are easy to get cheap! Ray.

Thanks Ray!
It's a real pleasure to get professional advice for an amateur like myself.
Please confirm that if he actually has the 750 ratio gears installed, they would clear the crankases?

[rapidray]

You have to remove material. I don't know what is involved first had with 8 valve cases but on 16 valve cases you only need to remove material from the cases where the front of the gear will hit the main web area. Ray.

[Agemax]

take a look at this thread John, this guy fitted 750 clutch in his Gs1000. you can see where he modified the top crankcase. not sure if that is over the top for drag racing or whether that is what is required to fit the bigger gear.

http://www.thegsresources.com/_forum/showthread.php?t=217781

[GregT]

John, I've come to this late but have you checked with Nova as to whether it actually is one of theirs ?
In my experience Nova usually try for a bolt in setup which doesn't involve machining cases. they may have done something which is a different ratio from either the 750 or 1100. Usually when they do a primary pair they supply both gears...

As far as whether it's worth straight cuts in a roadrace 8V motor - yes, it is. particularly if you're doing the IOM - as most of Nova's customers would be.

[nickp]

nova gears

the nova gears are all standard 1100/1000 ratio, and go in with no case mods on a gs1000. nick

[John Kat]

the nova gears are all standard 1100/1000 ratio, and go in with no case mods on a gs1000. nick

I wrote to Novaracing who were very kind to reply immediately and they confirmed that their gears require no modification to the engine cases...
My conclusion is that this crankshaft is fitted with GS 750 gears.
To me it's a no buy as I don't want to deeply modify the engine cases.
Thanks to everyone!

[patrino]

I'm a bit late to the party here, but after reading these posts am I right in thinking that the OEM 1100 primary drive gears are helical-cut (not straight-cut)?