Boring Stock Carbs?

[BigGuy]

Hey guys, I've been doing some digging on the topic of boring out the stock carbs. There doesn't seem to be a lot of conclusive info on here about this. I've gathered that they can be bored to 27.5mm max as per the slide diameter and the available stock in the carburetor throat. Some also mention that the slide seat must be deepened to allow the slide to shut off completely. my question is are any of you running this? Have any tried this? If so how were the results? I understand that simply upgrading to 28mm flat slides would be better but I can think of a few obvious advantages to modifying the stock ones too. First I already own a set in good working order, second I would not have to reinvent all the necessary cables and whatnot and lastly I'm a toolmaker by trade and have complete access to the required machines to do this at no cost to me. Offhand I'm thinking a wire EDM would be an ideal tool to open the throats. After that simply set up the carb bodies on a bridgeport, indicate the slide diameter and deepen the spotface? Obviously it sounds easy when you just say it (HaHa). I guess I'm just wondering what some of the talented builders on this great forum might have to say about this?

Thanks guys.

[WVWRZ500N]

Hey guys, I've been doing some digging on the topic of boring out the stock carbs. There doesn't seem to be a lot of conclusive info on here about this. I've gathered that they can be bored to 27.5mm max as per the slide diameter and the available stock in the carburetor throat. Some also mention that the slide seat must be deepened to allow the slide to shut off completely. my question is are any of you running this? Have any tried this? If so how were the results? I understand that simply upgrading to 28mm flat slides would be better but I can think of a few obvious advantages to modifying the stock ones too. First I already own a set in good working order, second I would not have to reinvent all the necessary cables and whatnot and lastly I'm a toolmaker by trade and have complete access to the required machines to do this at no cost to me. Offhand I'm thinking a wire EDM would be an ideal tool to open the throats. After that simply set up the carb bodies on a bridgeport, indicate the slide diameter and deepen the spotface? Obviously it sounds easy when you just say it (HaHa). I guess I'm just wondering what some of the talented builders on this great forum might have to say about this?

Thanks guys.

I've not performed the operation but those who have usually use a 4 jaw chuck on the lathe and offset the venturi that way and use a boring bar.

[begbie]

I'm pretty sure, Rick lance bores them oval.

[giron]

what happens if the stock carburetors are ruin when you bore them out? Does it make more sense to get 28mm? then sale your stock carburetors to off set the cost?

[silverstrom]

I agree. If you want bigger carbs, buy bigger carbs.

[ixe13]

I have a set of carbs that were overbored and now you can see the light on each side of the slide .

[BigGuy]

I have a set of carbs that were overbored and now you can see the light on each side of the slide .

I'm guessing whoever did these went too big and stayed on center?

[BigGuy]

Hey guys, I've been doing some digging on the topic of boring out the stock carbs. There doesn't seem to be a lot of conclusive info on here about this. I've gathered that they can be bored to 27.5mm max as per the slide diameter and the available stock in the carburetor throat. Some also mention that the slide seat must be deepened to allow the slide to shut off completely. my question is are any of you running this? Have any tried this? If so how were the results? I understand that simply upgrading to 28mm flat slides would be better but I can think of a few obvious advantages to modifying the stock ones too. First I already own a set in good working order, second I would not have to reinvent all the necessary cables and whatnot and lastly I'm a toolmaker by trade and have complete access to the required machines to do this at no cost to me. Offhand I'm thinking a wire EDM would be an ideal tool to open the throats. After that simply set up the carb bodies on a bridgeport, indicate the slide diameter and deepen the spotface? Obviously it sounds easy when you just say it (HaHa). I guess I'm just wondering what some of the talented builders on this great forum might have to say about this?

Thanks guys.

I've not performed the operation but those who have usually use a 4 jaw chuck on the lathe and offset the venturi that way and use a boring bar.

Hi Bill, this makes more sence, not having to mess around with the venturi or deepen the slide seat would be ideal. I'm going to have to figure out how big I can go with the offset approach.

[BigGuy]

what happens if the stock carburetors are ruin when you bore them out? Does it make more sense to get 28mm? then sale your stock carburetors to off set the cost?

Hi, I'm confident I can machine them to the targeted size and/or offset without error. I guess my question is even if I do this without fail how do these work in the end? As far as selling the stock carbs I (and possibly others on here?) tend to be guilty of collecting RZ parts rather than parting with them. Lol. Even if I get the 28s and put the stock ones aside it's not likely I will ever lace up the 26s again just because? If it was as simple as just buying the 28s and away you go than I would be all over it but from what I understand there is quite a bit of work involved in making them work? Like others on here I do enjoy modifying something I already have to suit my current needs but ultimately if they aren't going to work well than I guess it's all for not.

Thanks guys for all the replys! I'm not saying I'm set on this either way, just looking for some feedback on the possibility.

[giron]

Bill on these forums sell kits with cables. I have 28mm on my RZV500 with a stock engine and I'm happy with them. Also the 28mm give you more adjustments than the stock carburetors. Its funny a long time member on this forum always said. Look at a gamma and see how it was done

[BigGuy]

Bill on these forums sell kits with cables. I have 28mm on my RZV500 with a stock engine and I'm happy with them. Also the 28mm give you more adjustments than the stock carburetors. Its funny a long time member on this forum always said. Look at a gamma and see how it was done

Bill has already helped me out a bit with this project. He gave a me price to upgrade to the 28s and I'm sure it is a very fair number. He was great to deal with and quite knowledgeable. But even the fair number isn't small. This project started out as me just buying a set of pipes and throwing them on a bike that has been sitting in my garage for 12 years so I could ride it to work once and a while. After asking some questions and doing some reading it turns out there is a little more to it than that. Lol. I decided to take some of the good advice given and pull the motor to replace crank seals and go over everything. I found some things that I'm glad were not letf to chance. Well once you're in there you might as well keep going right? Next thing you know I have an RZV frame, fitting an R6 forks and swing, wheels to match, doing some porting, cranks getting rebuilt, zeeltronic ect... I know many of you have been through this but this is starting to add up $$$$$. I am trying to take the approach of focusing my efforts and $ on the big stuff first and maybe upgrading the carbs down the road a since they are kind of an external thing? If boring the stock carbs is a viable option it literally would not cost me a dollar to do so I'm just exploring the idea.

[vdrive]

Hey Big Guy , did the crank seals turn bad after sitting all those years ? please let me know , kind regards Andrew

[BigGuy]

Hi Andrew, to be honest they didn't at all? I am still going to relpace them of coarse. I did however find several other major gasket leaks during the test. I know its tempting to just leave them but I gotta think that the rubber can't be as supple as it shoud be an may not last as long as it should? I also found that the check valves on the auto pump had allowed some oil to drain into the crank case.

[vdrive]

Hey Big Guy , many thanks for the information , have a great week / weekend , kind regards Andrew

[BigGuy]

So is and/or has anybody run the bored out stock carbs on there bike? If so how did they work?