early t500 carbs on later model engine?

srech77 · Post by **srech77** » Sat Aug 02, 2014 7:37 pm

Wondering if anyone can speak to using the 34mm carbs on a 75 t500? I don't plan on doing this, necessarily, but I was reading "somewhere" that this can be like an upgrade if you have ported heads and chambers and require an increase fuel flow? Or just better off sticking with the 32mm Mikunis and rejetting ...

Any of that ring a bell ...

thanks -

argo1974 · Post by **argo1974** » Sun Aug 03, 2014 5:08 am

Fuel flow is not a problem, as this is an issue of how big are the jets, but bigger carbs help the engine breathe better at high revs. In case you will have the intakes ported, VM34-s are a great option, especially with Ivan's jetting kit. Stock Cobra VM34-s have a flat spot (lean mixture) right off the idle position.

srech77 · Post by **srech77** » Sun Aug 03, 2014 8:21 am

argo1974 wrote:Fuel flow is not a problem, as this is an issue of how big are the jets, but bigger carbs help the engine breathe better at high revs. In case you will have the intakes ported, VM34-s are a great option, especially with Ivan's jetting kit. Stock Cobra VM34-s have a flat spot (lean mixture) right off the idle position.

I see, so who is Ivan and where do I get his jet kits at? Also, I've read that the factory 32mm and 34mm carbs are not "true" VM carbs ... so do I need to pursue some of the newer round-slide VM34 mikunis, and try to rejet them for my bike ... or will a set of the older factory 34mm carbs do the trick?

thanks much -

srech77 · Post by **srech77** » Sun Aug 03, 2014 8:22 am

argo1974 wrote:Fuel flow is not a problem, as this is an issue of how big are the jets, but bigger carbs help the engine breathe better at high revs. In case you will have the intakes ported, VM34-s are a great option, especially with Ivan's jetting kit. Stock Cobra VM34-s have a flat spot (lean mixture) right off the idle position.

Also, I believe Eric is porting the intakes with the jugs, so that is something to consider ...

srech77 · Post by **srech77** » Sun Aug 03, 2014 8:26 am

Okay ... I found Ivan's Performance Website ... $370 is pretty steep for some rejetting and only a couple more ponies, no?! I guess the harder part is finding a good set of used 34mm carbs first, then figuring out how to fit them on a 75 bike with the newer air box, boots, etc.

tz375 · Post by **tz375** » Sun Aug 03, 2014 8:34 am

I think that Ivan's jet kit is designed to make a stock early model bike run a whole lot better than stock. It's not really a universal fix early carbs for every other combo kit AFAIK.

Stock OEM carbs are VM series in general design but they are cast in low cost pot metal which is heavier than aluminum and the air circuits are different too.

If you want to fit larger carbs I'd suggest getting aftermarket VMs and ask Eric for his jetting suggestions as a place to start. All motors are slightly different and yours will probably end up slightly different to Eric's starting suggestions.

With Jemco pipes and ported cylinders, fueling requirements will be a little different to stock. 32 to 34 is not a big change in size or performance, but if your OEM carbs are worn out maybe new 34s would be a good idea I wouldn't use OEM 34s though

srech77 · Post by **srech77** » Sun Aug 03, 2014 2:21 pm

tz375 wrote:I think that Ivan's jet kit is designed to make a stock early model bike run a whole lot better than stock. It's not really a universal fix early carbs for every other combo kit AFAIK.

Stock OEM carbs are VM series in general design but they are cast in low cost pot metal which is heavier than aluminum and the air circuits are different too.

If you want to fit larger carbs I'd suggest getting aftermarket VMs and ask Eric for his jetting suggestions as a place to start. All motors are slightly different and yours will probably end up slightly different to Eric's starting suggestions.

With Jemco pipes and ported cylinders, fueling requirements will be a little different to stock. 32 to 34 is not a big change in size or performance, but if your OEM carbs are worn out maybe new 34s would be a good idea I wouldn't use OEM 34s though

I see, that's helpful advice. I'll drop Eric a line and see what he thinks. My stock carbs are in pretty good shape for the most part, but like you said, with the porting, chambers, etc. it might be a noticeable difference to just buy new carbs and start playing with jets.

Also, I assume that buying the newer VMs requires the use of pods, as they probably don't match up between the stock air box and intake boots? I guess it's probably acceptable to run pods considering the engine modification anyway ...

tz375 · Post by **tz375** » Sun Aug 03, 2014 3:36 pm

Yes, it's a good idea to use individual filters (pods) as long as they are large and not those silly little imported things that restrict flow

srech77 · Post by **srech77** » Mon Aug 04, 2014 9:53 am

tz375 wrote:Yes, it's a good idea to use individual filters (pods) as long as they are large and not those silly little imported things that restrict flow

Do you have a link for a specific pod you are talking about ... I've used the foam UNIs in the past with good luck, I like them over the little K&N cones, but whatever works I guess. And what sort of setup have you run with success?

early t500 carbs on later model engine?

early t500 carbs on later model engine?

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Re: early t500 carbs on later model engine?

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