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1981 GSX1100 Katana Based Project

Haven't been on the forum for over half a year and it was quite a treat to read up on the project as well as seeing it's still going in 2025.
Happy new year's, mate! and best of luck keeping the tally below 200kg.
 
Diirk said:
Haven't been on the forum for over half a year and it was quite a treat to read up on the project as well as seeing it's still going in 2025.
Happy new year's, mate! and best of luck keeping the tally below 200kg.
Click to expand...

Hi Diirk, thanks mate and a Happy New Year to you. Yes, the build continues to get lighter, the next goal is to hit 199.00 kg. Finding 677 grams would be easy if I swapped the OEM indicators for LED units but then it wouldn't look right and if it doesn't look right it isn't right. Swapping mirrors could be an option?

Cheers mate.
 
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These M5, M6 and M8 aluminium bolts arrived today, they are to replace the titanium bolts currently holding the cowl brackets in place and a few other brackets that don't need Ti or steel to secure them. Much lighter than titanium or steel bolts so once installed the running tally will be adjusted.

Ally bolts 1 by Max Mutarn, on Flickr
 
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Just noticed in the pic before the aluminium bolts on the scale pic, the catch can support bracket needs to go on a diet. Must be around 25 grams extra weight there?
 
I remember when Harley boasted in their print ads the heft of their bikes. "A passing 18 wheeler is not going to blow you out of your lane," some thing like that.

Circa early 1970's, IIRC.
 
Rob S. said:
I remember when Harley boasted in their print ads the heft of their bikes. "A passing 18 wheeler is not going to blow you out of your lane," some thing like that.

Circa early 1970's, IIRC.
Click to expand...

Amusing that they even entertained the notion that a passing 18-wheeler would be overtaking a bike.
 
Shed a few more grams today by replaced some titanium bolts with aluminium bolts, not big savings but every gram taken off helps in the big picture.

ally bolts 1a by Max Mutarn, on Flickr


The aluminium cowl brackets were attached with titanium bolts, replaced them with aluminium allen bolts, much lighter.
ally brackets 1b by Max Mutarn, on Flickr

Also replaced the oil cooler lower deflector bolts with aluminium allen bolts, four bolts weighing 3 grams!

oil cooler defector bolts by Max Mutarn, on Flickr


Running tally = 199.585 kg.
 
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Nice carbs, but maybe slightly too big for your engine. I had 38 Mikunis on my 1296 cc GSX and they worked quite well. Then I swap the engine to 1360 cc and now the carbs are working perfectly.
I think the 34`s would have been better for you if you are not going to racing.
 
Blower said:
Nice carbs, but maybe slightly too big for your engine. I had 38 Mikunis on my 1296 cc GSX and they worked quite well. Then I swap the engine to 1360 cc and now the carbs are working perfectly.
I think the 34`s would have been better for you if you are not going to racing.
Click to expand...

Yes, maybe 34 mm flatslides would suit a stock 1135 and I know some who are running those carbs on their Kat. However, fitting 38 mm flatslides is not unusual with the 1135 and over engines in my part of the world. My engine will be running a set of 4-1 Yoshi 60 mm pipes with a 60 mm muffler, Yoshi cams, adjusted timing, velocity stacks and to get it sweet the carbs will be set up using an O2 sensor to sort out the jetting.

Right now the Kat is fitted with 36 mm CV carbs with 160 main jets and it is running strong and smooth in each gear all the way up to WOT.

The build focus is weight and not outright performance. If the flatslides are heavier than the 36 mm CV carbs that will pose a problem for me.
 
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I would be surprised if the flatslides aren't heavier as I've always found them to be "weightier" in my hands than their CV counterparts. But the scale will tell.
Regardless of the weight I'd switch them over because I feel that your end result shouldn't be all about weight, but how you enjoy the motorcycle as a whole. I highly doubt in any case that the carbs will tip you back over the 200kg so the mental aspect of it should still be acceptable :p
 
Diirk said:
I would be surprised if the flatslides aren't heavier as I've always found them to be "weightier" in my hands than their CV counterparts. But the scale will tell.
Regardless of the weight I'd switch them over because I feel that your end result shouldn't be all about weight, but how you enjoy the motorcycle as a whole. I highly doubt in any case that the carbs will tip you back over the 200kg so the mental aspect of it should still be acceptable :p
Click to expand...

The numbers are in and it isn't looking good for the flatslides.

The 38mm flatslides, two throttle cables and twin cable throttle = 4,140 g.

The 36 mm CV's, one cable and single cable throttle = 3,172 g.

So changing to the flatslides will add 968 g (and about 10 ponies going by dyno figures from previous 38 mm flatslides fitted to the 1135 engine) and take the weight up to 200.553 kg.

The raw numbers don't tell the full story, the elephant in the room is of course the extra performance of the 38 mm flatslides when compared to the 36 mm CV carbs. However, the Kat being 60 kg lighter than stock, the 36 mm carb jetting set up using an O2 sensor, the Yoshi cams and adjusted timing the Kat is plenty fast enough and has arm stretching acceleration in every gear. The balance and handling are excellent as is the comfort and seating position, for me this is everything I had hoped the project end result to be. So as it stands now, I am very happy with how the Kat rides and performs so I'll put the 38 mm flatslides away for now and keep on enjoying the Kat with the 36 mm CV's. Maybe oneday the 38's will get a run, but not today.

Running tally = 199.585 kg.
 
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