1275 to Ribcase

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1275 to Ribcase

Postby SerIIalpine » Tue Oct 06, 2009 5:16 pm

I am swapping my 1098 engine w/ Ribcase to a 1275 that came with a smooth case. I want to keep the rib case of course (the smooth is messed up anyway!) but I am having pressure plate issues. The 1275 has a smaller pressure plate, both in diameter and depth, and when I connect it to the rib case the arm from the clutch slave doesn't travel far enough to actuate the clutch. Do I need a new pressure plate (Moss Part #190-980 is what I am assuming), a new slave rod, or what? Any help would be appreciated! Thanks.
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Re: 1275 to Ribcase

Postby hpmowog » Tue Oct 06, 2009 5:52 pm

If you have the correct 1275 pressure plate, I suspect that your problem may be with the release bearing. The 1098 and 1275 release bearings have different lengths. The slave cylinders and slave cylinder pushrods are different as well. What parts do you presently have from each engine/gearbox combo?
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Re: 1275 to Ribcase

Postby Sprite33 » Tue Oct 06, 2009 7:38 pm

I run a 1275 clutch on my 1098. I use a 1098 aluminum flywheel that is drilled to accept the 1275 pressure plate. I had to use a 1275 throwout bearing and a 1275 slave push rod and both differ from the 1098. The 1275 slave has a different bore than the 1098 but I don't know if it is required to switch them. I did because I wanted a new slave when I converted. I am fairly certain that the clutch release lever is the same for both.
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Re: 1275 to Ribcase

Postby Bugzy59 » Wed Oct 07, 2009 10:12 pm

I have been through this. I use a 1098 flywheel on my 948 with ribcase. You should use a 1275 throwout bearing since it has the most offset. Either slave cylinder will work. The question is the pushrod length. The slave travel is about 3/4 inch. You want a pushrod long enough so that it well into the slave when the throwout hits the pressure plate. The 1275 pushrod works for me.
There are 3 styles of clutch forks. The ribcase/1275 has the most offset and is the preferable for your setup.
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Re: 1275 to Ribcase

Postby Ragnars-Frogeye » Fri Nov 06, 2009 10:19 am

Hallo from Germany,
I use an early 1098 (10cc) engine in my frog, with a 1275 clutch and a smooth box (9CG).
The clutch withdrawal lever is different. You can't use the one from the smooth box for a rib case! I also had to change the release bearing itself, as it's different too - it must be the one for the 1275.
There was no need to change the slave cylinder.
If you have all the correct items it normally works. Sometimes the withdrawal lever hasn't the right curve after many years of work. So you must bend it a little in the right direction.
Someone told me to take hammer and a piece of would and than with a short blow it works. I've never done it myself! I could be done in the car, after taking it off the slave cylinder.

@ Bugzy59 you wrote about the travel of 3/4 inch. did you measure it or is it mentioned in a book? I ask because I'm looking for those dates.
Greetings from Germany

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Re: 1275 to Ribcase

Postby Bugzy59 » Sat Nov 14, 2009 12:49 pm

3/4 inch is my estimate from eyeballing it. I recall an earlier thread - "which slave cylinder" where the specs were set out. Let me know if you have trouble finding it.
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