Carbs for 1015cc or 1075cc Upgrade

I'm considering the APE 1015 or 1075 kits and was curious what carbs are typically used when upgrading to these.

I currently have the stock Mikuni 26's on my '76 Kz900-A4.

For a 1015 or 1075 your best all around performance is the Mikuni 29mm smooth bores. They are easy to maintane and provide power over a wide rpm range. Now days used one cost more then they did new out of the box. Anything bigger on a motor that size will hurt your performance and waste your money. Your intake port is appx. 30mm in diameter almost a direct fit for the 29's. This would allow you to have a high port velecity in fill your cylinders.......

i am going to run my vm26ss with my 1075 kit....i had my bike running with kit and it revved up well.....awaiting the return of my carbs from wg..
had an idle problem.....i expect my combo to be fairly responsive at low rpm s up to factory redline....i really wont know untill i get carbs back
and actually run it down the road.....just my .02....keith

I run CV 34s with my built 1150 GPz with a stage two kit installed. These carbs came stock on everything from a kz750 to the 1100 and work really grate. The best part is that you will also see an increase in fuel efficiency. You will go from about 36mpg (this is what I get on my stock 76 KZ900) to almost 50mpg. Install a stage 1 or stage 2 DynoJet kit and you will get all the response and power that that motor can provide. You can get a set of BS34 CV carbs on eBay for around $150, and the dynojet kit will cost about another $100. This combo was fantastic on my stock 81 KZ1000 and works great on my built GPz1150.

Otto

On the stock 1015 motor with 26's you run out of top end pretty quick. The 29's are perfect for 1075 to 1105 motors with a decent set of cams.

Thanks guys!

go with the 29smoothies the differance between the 29's and 26's is amazing i'll use what i learnt at the track the beast i went with my 1075 street bike with the 26's was 11.60 at 112 mph with the 29's on the same weekend i went 10.82 121mph and ridding around town it is also more responsive by a bunch they definitly wake up a 1075 kit.

I have to agree with what tirebomb said. If you even can find a set of 28s much cheaper than the 29's as it seems they all go for 500 these days and up. I guess the downside to the z1 28s is that the linkage is not great and it's hard to tune them just right. I heard that from a mechanic but personally I do not know. The keihin 29 race carbs I have heard good things about as well and they are new for a buck more maybe it would be better than the old need to be rebuilt 29's. You never know with those old carbs as they may have been butchered or may need rebuilding in which case I would say find some newer 29's from keihin or buy em new. I don't think Mic makes any 29s any more you would probably have to go with the 34's which I hear are not to great for anything under 1200 and have a smooth idle response down low. I dunno.
I do know that my bike from 26 to 29 woh! What an improvement and then you add the comp baffle (better and louder than stock baffle and faster than open pipe unless you are draggin it) to the V&H and the bike goes really nice big improvement over stock baffle.
I have some 28's from my 80 I am not using but they are pumpers and I don't know how well they work as I took them off the minute I got the bike and I never used them. I may sell them soon or keep them in case later on down the road they will come in handy. So if kaw changed them on the 80s must be because the 26's were too small.Originally they were 28's. The throttle response on my 29's is great. I run my buddies with stock carbs and they ask me if I had motor work done cause I kill them every time. lol I wouldn't go that far but they feel much noticeably different than the 26's I would never go back to that setup ever again. Go bigger! But not too big.

otakar wrote:

I run CV 34s with my built 1150 GPz with a stage two kit installed. These carbs came stock on everything from a kz750 to the 1100 and work really grate. The best part is that you will also see an increase in fuel efficiency. You will go from about 36mpg (this is what I get on my stock 76 KZ900) to almost 50mpg. Install a stage 1 or stage 2 DynoJet kit and you will get all the response and power that that motor can provide. You can get a set of BS34 CV carbs on eBay for around $150, and the dynojet kit will cost about another $100. This combo was fantastic on my stock 81 KZ1000 and works great on my built GPz1150.

Otto

Those are better for that bike because the head breathes better am I right? He would have to get some serious head work done to make 34's run well with a 1075 on a non J motor or am I mistaken?
When are we going to get togeteher for a ride? I am waiting now for my bike to get the head and block back from the machine shop to get her running but I have the option of riding my friends Kaw. I hear it will hit 63 by the middle of the week. Well, it can't be too long before we get nice weather.

The best part about the CVs is that they deliver only as much as the engine can handle. They are not a true 34, because they venturi down, unlike smooth bores (hence the name)doing the cross sectional math across the center of the venturi. They have the area of a 31.2mm round hole but because they are a true venturi they accelerate the air better and in turn draw fuel better. With the vacuum venturi opened to the top diaphragm you can make them respond as much as you want by the size of the hole.

the bs 34's are a good working carb as well there are still dyno jet kits available for tuning its not bad to go with one of those just because of the needles they come with but on the down side you do have to go with intake manifolds as there are quite a bit bigger physiclly. so that will be extra monet and extra work to match the ports to the manifolds so if your going that route i would get the head ported at the same time.

If someone is going to all the trouble to punch out a Jug and is looking for carbs to supply the air it needs, not porting the head, is like taking the time and expense to train a thorough bread race horse and than tying its back two legs together for the Kentucky Derby. Why bother to do all the work to begin with. Read Cavanaughs web sight, you'll understand. www.flowbenchtech.com/porting/CRH/kz-data.htm