Clairity in pictures, my Keihin CR carb questions.

[LT]

Hello,

Thanks for bearing with me on my learning curve (we all go through it). Here are three pics of a Keihin CR Special 39mm paired carbs I'm installing on a 1997 Suzuki GS500.

I have a factory manual for the stock carbs, but that is of little help for this new Keihin.

In the pictures I'm wondering what certain doo-hickeys and orifices might be for.

I've gotten a suggestion already from one gracious member with further questions for me to answer. Being the ignorant uneducated newby, I decided to let a picture say a thousand words (and ask a few questions).

Any and all comments/answers/pointers are greatly appreciated.

[sickpup]

39mm are to big for this engine unless you are racing.

[Barry_M2]

The tubes you labeled for balancing, look to be overflows for the choke mechanism.

The 'Goop' that was put on at the factory is just to block the holes as they are seperate carbs, joined together, and can be use as a single, twin, triple or quad setup etc....

The other 4 holes are probably adjusters for air jet, are there small screws inside?

[Kickstart]

Hi

I don't think those are take off points for balancing the carbs. Look to me that they go into a pipe cast into the carb body (possibly the choke mechanism).

The goop on the end looks like it is just there to block the fuel rail. I presume that the carbs come from Japan but the bars linking them together are designed, sourced and installed by your Keihin importer. I expect that it would be quite possible to have (say) 4 carbs joined together with a pipe between each of those ports on the carbs to supply fuel, with a single pipe from the fuel tank to one of them.

Not sure about the spare bits you mention. However carbs are often designed and cast for use in a fair range of engine with different machining. Entirely possible that those are (for example) a port to connect a 2 stroke oil pipe to, or a power jet, and is just not machined for use on these ones.

As to Sickpups comments, he may well be right. I have a set of 40mm Mikuni flat slides to go onto my 1200 Bandit. Pretty similar to what you have there. But my Bandit has been tuned a bit (currently producing just under 150hp at the back wheel running on the stock 36mm CV carbs) and that is borderline for using 40mm slide carbs.

All the best

Keith
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[sickpup]

I'd use the 36 or 38 with the Bandit head and 38-40 on the GSXR11K/L preferably the 38mm myself. The 40mm are really to big unless you want outright power.

[Kickstart]

[sickpup]

The 40's will be fine but you will lose a huge amount of mid range.

The 38's would keep a large chunk of that mid range and probably have the same top end. People go for the 40's as they feel more powerfull.

Seeing dyno charts at Ken coopers when he tried 36-38-40mm on a drag bike was quite surprising. The 36's only produced a few ponies less than the 40's at the top but a better spread everywhere else.

Each to their on though. I know many tuners swear by the 40's.

[Kickstart]

Hi

I will see how they go. The Bandit is not short of mid range, but I might hate the setup with the 40mm slide carbs (and the throttle is likely to be a hell of a lot heavier). Target is to get it over a genuine 170mph (so time to play with the gearing as well) without a fairing.

All the best

Keith
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[sickpup]

Either PDQ or TTS tried this with a BAndit and had real problems with air flow.

Basically using trumpets without an airbox at that speed the air pressure outside the carbs was lower than the air pressure drop in the cylinders as the pistons moved down so it couldn't suck in any air although on a static Dyno the speed recorded was in excess of 170mph. This is one of the problems with Dynos that I've found, they can't simulate real world air pressure at all.

Did they modify the crank case webbings when they did the work on your lump?

[Kickstart]

Hi

That is one concern I have about the top speed with the new carbs and dropping the airbox (I am currently running the stock carbs with a dynojet kit, with the airbox and a K&N filter with the lid chopped off the airbox, result was 166.2mph), although there is a guy on a US Bandit site with a similar setup who has managed a measured 180mph. One reason why I am not prepared to do anything that cannot be reversed. I can always stick the stock carbs and airbox back on. I am contemplating making up some kind of enclosure for the carb inlets.

I know that the FZ750 / FZR1000 can suffer in a similar way if they are run without an airbox.

Nothing was done inside the actual crankcases (reason for sticking at 1216, going much larger than that means machining out the crankcase openings).

Just been thinking. The bike is a touch down on power now compared to when the engine was built. Have a feeling that might be down to the chain. Think it has been on there about 16k and although it has not really needed adjusting much and the rear sprocket looks OK I haven't checked the front for ages. Have a feeling that it might be rather more worn, and there seems to be some harshness to the transmission at the moment. Job for the weekend (and if I replace them then I will order a selection of sprockets).

All the best

Keith
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[sickpup]

Have a think about carving pumping holes between the webs of 1-2 and 3-4 as the pumping losses are huge at high RPM's and more importantly you don't want to pump the oil out through the breather. For some reason a lot of relatively standard 1216's suffer over pressure within the crankcases.

[Kickstart]

Hi

Not sure I want to push this engine much more and it has had no problems yet (done ~10k since the engine was done). If I go far enough to open the cases up then it will probably land up being rather more than 1216cc .

More likely I will just buy a 'busa or ZX12R later this year for frightening myself. Or be cheap and buy a GSXR1100 to play with.

All the best

Keith
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