Katana with a GS850 engine

[AJs Adv]

Hi guys

I came across a Katana frame (650) with a GS850G engine. What are your thoughts on this? Is it a viable combo? At first I thought no way, but the idea is intriguing me more and more. It is going very cheap - as usual the owner claims the carbs need to be synchronized - the cosmetics are in really good condition and I read that the 850 engine is almost bullet proof.

Will appreciate any advice/thoughts thanks

[rphillips]

This may be a dumb question, but, How is the driveshaft from the 850 connected to the chain & sprocket on the Kat frame??????

[Steve]

This may be a dumb question, but, How is the driveshaft from the 850 connected to the chain & sprocket on the Kat frame??????

The 650 Kat was a shaftie.


They must have had a VERY GOOD shoehorn to fit the 850 engine in the 650 frame.

Not sure about just the engine, but the whole 850 is about 100 pounds heavier than the 650, I am sure that a bunch of that 100 pounds is engine and the frame needed to support it. Although they evidently got it to fit, I would question the structural integrity of the package.

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[Dogma]

The 650 Kat was a shaftie.


They must have had a VERY GOOD shoehorn to fit the 850 engine in the 650 frame.

Not sure about just the engine, but the whole 850 is about 100 pounds heavier than the 650, I am sure that a bunch of that 100 pounds is engine and the frame needed to support it. Although they evidently got it to fit, I would question the structural integrity of the package.

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Well, folks put 1100s into 750 frames. It might be a little flexy, but I doubt it will break. Sounds like a fun combo, if it all works.

Not seeing pics of the setup, I'm guessing it has pod filters since the stock airbox probably wouldn't line up to the 850's carbs. It wouldn't breath properly though the 650 box anyway. Hopefully it has some kind of 850 size exhaust too. Hopefully after that, it's been properly jetted for all that. Now then, if the current owner could do all that correctly, he probably could have balanced the carbs. I'm thinking this is an unfinished project bike. Expect to do significant tuning.

[AJs Adv]

Here is a picture of the set-up - it does look like a really tight fit and you cannot not really see what he did with the carbs.

If the frame can handle the extra power without flexing too much and becoming dangerous I am quite willing to do the extra work required

[Steve]

Expect to do significant tuning.

That is "standard procedure", even if the 'new' bike is perfectly stock.

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[Steve]

I am wondering what his motivation was for the project.

A stock 650 is rated at about 73 hp.

A stock 850 is rated at about 78 hp.

Not much more power for all the weight added and effort involved.

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[Dogma]

That is "standard procedure", even if the 'new' bike is perfectly stock.

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Well, by significant tuning I mean rejetting and other adjustments, above and beyond what's needed for stock.

[Dogma]

Here is a picture of the set-up - it does look like a really tight fit and you cannot not really see what he did with the carbs.

If the frame can handle the extra power without flexing too much and becoming dangerous I am quite willing to do the extra work required

Interesting. It looks as though the front brakes have been upgraded. It's hard to be sure in the blurry photo, but those don't look like stock calipers, rotors and master. I'm not sure that isn't the 850's front wheel. Didn't the 650M have the tri-spoke pattern?

As Steve pointed out, it's not a big gain in power for stock motors. Maybe he got bored, or torched the 650 and only had an 850 around. Who knows? With pods and pipe that 850 might be making a few more than stock (assuming correct jetting). Either way, it's not an enormous increase in power. I wouldn't expect it to be dangerous. Well, not any more dangerous than the rider.

I would say to get it if it strikes your fancy. It doesn't have to make sense to anyone else. Just be aware that a significantly modded bike might still be a project.

[Dogma]

That is "standard procedure", even if the 'new' bike is perfectly stock.

.

Well, by significant tuning I mean rejetting and other adjustments, above and beyond what's needed for stock.

[Sandy]

If the 850 motor is taller than the 650 you might want to check if you can get the valve cover off without dropping the motor in the frame or having to remove it entirely for valve adjustments. That would be the ultimate PITA. The 650 motor has a plain bearing crank while the 850 is roller bearing, it will be a much heavier lump so frame strength and suspension should be also taken into consideration. It could work, there are a lot stranger engine conversions out there.

[AJs Adv]

It seems the current owner did not like all the questions - he seems to have gone to ground hahahaha. Thanks very much for the advice and comments. I will post again if he decides to surface