Thundercat Engine

[Danny]

It must fit a 1998 model Thundercat, the lower the milage the better.

Please e-mail [email protected] with offers.

[Phoenix]

What've you done to your engine Danny?

[Danny]

2nd gear has decided it didn't like cogs and prefers a rounder look.

[carvell]

So replace the gears in question?

No need for a new engine I wouldn't have thought?
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Yamaha TDM 850

[tatters]

[Danny]

tatters is right, it's more expensive to fix the engine than swap it, especially when you consider it needs a major service (£300-600).

[Kickstart]

Hi

Ouch Danny.

To be honest I would be half tempted to fix it, as the replacement could have the same problem.

And when the engine is out it is easy to do the valves.

Added to which for years Yamaha engine and frame numbers matched, so a replacement engine is easy to spot.

If you are not unlucky then it will be quicker to just swap the engine.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Danny]

Keith, thanks for your insight into this matter.

I am now looking into fixing the engine and fitting a Factory Pro Shift Kit to help prevent it happening again. I've found a shop over the pond that sells the kits for $70, I'm just waiting for a quote for the rest of the parts.

Got any free weekends coming up?

[Kickstart]

Hi

Excuse my ignorance, but what is the factory pro kit? What does it do?

Think the little FZR based lump is quite light. Should be fairly easy to drop out. A reasonable compromise if you do not fancy diving into the engine yourself is to drop it out and just take the engine in somewhere.

I would have to check the manual but I suspect you need to completely strip the engine to fix the gearbox (the old FZ750 engine and its derivatives have some of the bolts holding the crankcases together under the barrels so you cannot just take off the bottom of the cases).

Doing the valves with the engine out should be easy. Probably worth lobbing another cam chain in there at the same time. There are a few other things that may be worth replacing at the same time (not sure on the 'cat engine), such as the bearing behind the front sprocket (weak point on the larger engines) and the starter clutch (not that weak, just a nightmare to replace).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Danny]

From what I've read the shift kit is supposed to make gear changing quicker and easier; the main benefit for me would be that it helps prevent gears failing like this (or so everyone claims on the Thundercat forum).
https://www.factorypro.com/products/shift.html

I believe it is a complete strip down to change the gears as you say.
If your feeling a bit bored feel free to look through the workshop manual:
https://www.thundercat.nl/index.php?option=com_docman&task=docclick&Itemid=42&bid=24&limitstart=0&limit=30

I'll call around some local garages and see how much they want to just fix the loose engine, but I'd expect it to be around £300-400 (£100 less than a replacement engine).

[Kickstart]

Hi

Looks like it is just better quality shift components. Might well improve things.

2nd always seems to get the worst hammering of any of the gears. Personally I tend to baby it a bit more into 2nd than any other gear.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Danny]

I got a quote for the parts, £280 for OEM parts plus at least £100 for preventative maintenance. So I'm going to get a replacement engine and fix the old when as and when parts come up on eBay.

[Kickstart]

Hi

Fair enough. Swapping the engine should be fairly quick.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Jrod]

[Kickstart]

Hi

Possibly, although it is also the most heavily used change and has plenty of torque going through it.

Technically there is a neutral between every gear, not that you should ever be able to find them. Otherwise you could engage 2 gears at once with rather nasty consequences.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing