1981 GSX1100 Katana Based Project

[Shin-Ken 1074]

A parcel arrived today.


Mikuni by Max Mutarn, on Flickr


A set of new Mikuni RS 38MM flatslide carbs for the project Kat. Not only would they be helpful in providing some get up and go, they are an amazing looking bit of kit and could well be considered Art!


Mikuni 38 mm a by Max Mutarn, on Flickr


Mikuni 38mm b by Max Mutarn, on Flickr

[Grimly]

Lovely stuff. ............

[Blower]

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.

[Shin-Ken 1074]

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.

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.

[Diirk]

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

[Shin-Ken 1074]

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

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.

[first timer]

just go to the bathroom before you ride the kat with 38's that will get you back to base

[Blower]

Install Bandit 1200 cylinder liners on the original cylinder block and bore them for gen.2 Hayabusa pistons. You will save at least the weight difference of the RS Mikuni, the engine capacity will increase to 1360cc and the torque & power will increase nicely.

[Shin-Ken 1074]

just go to the bathroom before you ride the kat with 38's that will get you back to base

Good thinkin' 99, there are no wrong ideas here.

[Shin-Ken 1074]

Install Bandit 1200 cylinder liners on the original cylinder block and bore them for gen.2 Hayabusa pistons. You will save at least the weight difference of the RS Mikuni, the engine capacity will increase to 1360cc and the torque & power will increase nicely.

Yep, for converting an old Kat into a Hotrod that is one way to go for performance and perhaps shedding a few grams. Would be interesting to know how much lighter the Gen 2 Busa pistons are compared to aftermarket forged pistons?

[Rob S.]

Will anyone venture a guesstimate as to the quarter mile times? With over a hundred pounds shed, she must be in the low 10's.

[Shin-Ken 1074]

Will anyone venture a guesstimate as to the quarter mile times? With over a hundred pounds shed, she must be in the low 10's.

With a final drive ratio of 2.82 and one hundred and thirty two pounds lighter than Factory specified curb weight.