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borus

1982 Tr80 350 Cush Drive

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I've rebuilt the motor and was surprised to see such a large counter weight / flywheel on the cush drive. My 1972 Mar 250 has no counter weight. Any one experimented with removing or reducing this extra weight? Looking at it it almost strikes me that it's a factory add on for those who wanted to tame the bike in the day? bike runs fine, just looking to put a bit of snap into it. this seems to be an obvious but need to get a little insight first.

cheers

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The weights were standard fitment on the Grippers, both 250 and 350.

From memory, you can't just remove the weight and leave the cushdrive as it's designed to fit together. I think you have to fit a complete cushdrive from a MAR to run a cushdrive without the weight. The spline that is a tapered fit on the crankshaft is a different length on the MAR.

However, the 350 should have plenty of snap with the weight in place, if it's sluggish to pick up there's something wrong. It should be fine with the weight on.

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The weights were standard fitment on the Grippers, both 250 and 350.

From memory, you can't just remove the weight and leave the cushdrive as it's designed to fit together. I think you have to fit a complete cushdrive from a MAR to run a cushdrive without the weight. The spline that is a tapered fit on the crankshaft is a different length on the MAR.

However, the 350 should have plenty of snap with the weight in place, if it's sluggish to pick up there's something wrong. It should be fine with the weight on.

good to know that the cush weight is standard, I'll look more at the jetting and exhaust etc. Seems to have a blast of power around midrange so I've got some sorting to do. Using a OKO 28 which worked well on my 250 Mar and a friends 350 MAR.

thanks

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Not yet tried an OKO on the Gripper so can't help with that specifically. I have one on the 350 MAR and it is fine but as the Gripper is ported differently I guess the jetting would be different.

What I forgot to mention is the head spacer, as they come in sizes from 0.5mm (or probably less) to 3mm thickness. Not sure what would be standard. My 350 Gripper, which I bought to renovate, has so much compression I can stand on the kickstart at TDC and it won't go over (and I'm 240 pounds approx) It's an absolute bitch to kickstart and is quite fiery off the throttle. When I get around to sorting it out I think a thicker spacer will be required...

Possibly, yours may have a thick spacer which will soften it off with the reduced compression. Bit of a pain to check but may be worth a look (assuming everything else is in order such as timing, etc)

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My head gasket is .5mm. Motor just rebuilt so I should be good there, felt stronger today, maybe a bit of runnin is needed???. I'll double check the timing. Starts first kick. I don't have the compression that you're talking about but it's a fairly strong kick required. I have Rock shocks on, so far I'm pleasantly surprised at how good the back end is. Front end still needs to be dialed in. Totally different bike from my MAR

cheers

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Yes, with a pair of good shocks working correctly, the back end works very well and Ossa front forks (Betors) are very good too.

Many people don't rate the Grippers. I jhaven't had enough time on one to judge really, I've ridden a few, briefly, but most have been dogs. The one I have now is the fieryest I've tried yet. I love the MAR but it stuggles against 80s twinshocks when sections get bigger or more technical. Maybe the ultimate would be the MAR chassis with Gripper suspension and 350 Gripper motor...

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Hi Woody

Just want to double check on some things:

MAR requirements:

fork oil - 200cc

tranny oil - 900cc

plug - B8ES NGK

I would think the tranny would be a little less due to the left side case being smaller, my bike came with a B6ES in it? I'm running a B8ES right now. Are the fork capacities the same, can't see why they would be different?

Also concerning pegs, I did move mine lower and back, much better.

I see Vitale (Spain) has a induction can on a gripper, I might try that eventually. Certainly lots of room to install one. I had one on a Italjet way back when it it was a very nice addition.

cheers

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Forks, MAR or Gripper I use between 180 - 200cc, usually 10W. Gear oil, yes, around 900cc on either. For plugs I generally use BP7ES in most bikes, never had any problems with them.

I've seen the article on the Vitale bike with induction can. Never tried one on anything, but that is one ugly bike with all the mods... I bought a 250 Gripper many years ago that had a '74 reed valve Phantom barrel/head 'grafted' on. It was a mess (the fit to the Gripper, not the reed conversion) and didn't work well at all. Put it back to standard but it never ran right so I sold it. There's an article on the net somewhere about a 250 Gripper that Joel Corroy converted to reed valve using a MAR barrel.

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Hi woody

Just a follow up, oko 28 works great, mid clip and 50 pilot. all sorted and tons of power but manageable. Starts first kick and using the .5mm head gasket. Thanks for the help. :thumbup:

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Thanks, useful info to know.

I've just been dismantling my 350 engine today but got stuck with the cush drive sleeve. It won't budge on this one and I've bent two 3-legged pullers already. Retired after conceding round 1, I'll have to fight it again another day. Fed up of it for now...

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Thanks, useful info to know.

I've just been dismantling my 350 engine today but got stuck with the cush drive sleeve. It won't budge on this one and I've bent two 3-legged pullers already. Retired after conceding round 1, I'll have to fight it again another day. Fed up of it for now...

had the same issue with my cush drive, between the better power, great suspension and more ground clearance it's making my practice sections easier than on the MAR, early days though...

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Hi ... just to resurrect this topic. I am looking at machining down a spare cush drive flyweight  to allow me to simply remove the existing weight and fit the machined down weight without any further mods... Will this work.

Also puzzled on a clutch problem... Is the clutch more prone to slip with lighter oil than heavier oil ?? 

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I had the cush flywheel lightened hacksawd it then finished it on the lathe, love the extra zip and i dont think i lost much low down torque.         I find i have to use every day multi grade oil in the clutch 20/50 Steve.

 

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