BDT 38mm carbs on a GS 1150

[jstewart]

Joe I would liked to try the 38 CV's on my 1150. The set of 89 GSXR 38's I bought on the GSXR forum were cheap ($150) so I didn't lose to much. They were advertised as completely disassembled but all there. The seller sells a lot of stuff over there and suggested these carbs be sent to another GSXR forum member who rebuilds a lot of carbs for GSXR forum members. The rebuilder has a excellent reputation with other GSXR forum members and no negative feedback on that forum. I bought the carbs and had the seller send the carbs directly to the rebuilder he recommended for cleaning, assembly and repair if necessary. The carb rebuilder the seller recommended called me 4 weeks later and said this set of 38's could not be assembled because of damage to the throttle shaft/butterfly parts and other issues that made them not worth putting any more money into. Nice guy, he didn't charge me anything. I had him send the carbs back to the seller and contacted the seller about refunding my money. The seller who recommended this carb rebuilder responded that he thought the rebuilder may have damaged the carbs trying to assemble them and he was going to send the carbs to a professional carb rebuilder for evaluation. That was 6 weeks ago and no further response.


I just decided that it was probably more effort and expense to find a good set of GSXR 38mm CV's and then tune them for my 1150 than I am willing to expend. I sonic cleaned, rebuilt, and painted my stock CV carbs and bought a new set of Mickuni 36 flat slides. I am a member of the vintage Japanese motorcycle club and when I want to show the bike at VJMC events I will use the stock carbs/airbox and stock exhaust system and for general street fun run the V&H header and the 36mm flatslide carbs.

Rapidray I would have rather bought a new set of Kehin side draft flat slides but they are no longer available and I could not find a used set smaller than 41mm which are just to big for my application on the street.

Thats too bad, I have had good and bad experiences. Been burned on evil bay more than once!
But I still think is WAY better now than years ago, finding info and parts way back when was interesting for sure!!!

I am running 38mm cv gsxr carbs on my 1150, I had 36 RS's and still wish I had them!
The street manners of the 38mm cv is better for sure at low rpm, low speed around town stuff, they are more forgiving with ham fisted operation also.
The 38 cv I have had a standard dyno jet kit for the GSXR750 when I got them. I had to buy new needle jets and I then switched to Factory Pro jet kit, they make a kit specifically for running 38mm cv's on the 1100/1150. It worked MUCH better but Im still to rich in the midrange. It wants 150 mains but then the needle ends up at full lean lowest clip position! If I run 130 mains the midrange is much better but its really lean on top! It's driving me a bit crazy.
Factory Pro suggests removing the stock air jet, re-tapping it to more common mikuni air jet size and putting in one .2mm smaller than stock.
I also have been thinking of really lowering the float height which may help some seeing the carbs don't sit exactly as they would on a gsxr.

So I was hoping for some good advice……. Maybe I should buy some RS's

 

[Joe H]

I actually would recommend them even with the problems I am having. chef1366 is a good resource, he offered some great advice and will provide the services if needed. I am debating another rebuild, if I knew a couple years ago what I leaned in the past few days I could have saved myself a lot of trouble and some money!
They defiantly have better manners around town than the RS 36's (but the rs's were not bad just not as smooth) the 38's also pull very strong down low when the emulsion tubes are good ( I call them jet needles ?? don't know why??) but the RS's had a more liner directly connected to the wrist feel and sounded way cool!


So the two main draw backs of theses 38's from my limited understanding are slide guide wear and emulsion tube wear and they are linked so if I would have known that I would have replaced theses parts at the same time.
When I replaced the emulation tubes a couple years ago it was great, very crisp throttle, great manners I was happy. I had made some mods to motor, going to a 1260 piston and some shorter duration cams, so theres more than one factor in play here, which never helps diagnosis!
I am going to take a look as soon as I get some time and check the wear on the slides and tubes again, seems like that those may be the suspect as to why they seem so difficult to tune.

 

[jstewart]

So the two main draw backs of theses 38's from my limited understanding are slide guide wear and emulsion tube wear and they are linked so if I would have known that I would have replaced theses parts at the same time.
When I replaced the emulation tubes a couple years ago it was great, very crisp throttle, great manners I was happy. I had made some mods to motor, going to a 1260 piston and some shorter duration cams, so theres more than one factor in play here, which never helps diagnosis!
I am going to take a look as soon as I get some time and check the wear on the slides and tubes again, seems like that those may be the suspect as to why they seem so difficult to tune.

So where do you get replacement slides & emulsion tubes????? Are the replacement parts new or are you taking your chances in the used parts market? The slides are not listed as available from Suzuki and I don't think the emulsion tubes are either.

 

[Guest]

I have a source for the slide guides.

 

[limeex2]

I picked up a set of 36's from a member , and had them rebuilt by a member. Have not had a chance to run them yet. Nice to know someone with lots of experience is here for help. 2-3 weeks hopefully, I should be able to burn some fossil fuel.

 

[Joe H]

So where do you get replacement slides & emulsion tubes????? Are the replacement parts new or are you taking your chances in the used parts market? The slides are not listed as available from Suzuki and I don't think the emulsion tubes are either.

I bought the emulsion tubes through bike bandit if I remember correctly, they should still be available, they are listed.
I think the DJ kit comes with emulsion tubes also, but not slide guides.
The slides are not listed anywhere on OEM stuff.
Bigger question for me is if the tubes are worn then it would suggest the needles would be worn also, to some extent. The emulsion tubes where around 30 bucks each, you can buy the entire DJ kit with the tubes for just a bit more.

My R/R is shot now so I may also take the time to check the wear on the slides and tubes again now that I have to dive into it, I am actually hoping they are bad it would explain a lot!

 

[Carter Turk]

I've have some chubby blunt DJ needles that came with the 36mm BST's I bought used. When I kept fouling plugs, I bought a Factory jet kit, still fouled plugs, then I heard about the emulsion tubes ovaling out. So I replaced those and finally had bike that ran on 4 cylinders. Later I changed all the 0-rings and my mileage improved by 10 mpg. There's also an 0-ring under the plastic slide guide that can easily be overlooked. Mine were all smashed and showing early signs of cracking, maybe presenting a richer condition than ideal.

 

[Joe H]

Thought I would post some pics of the worn slide glides on the BDT38's I have. The emulsion tubes are worn out again and after only about 2000 miles? because of the guides! I would have liked to post some pics of the tubes but I don't have any way to take anything but cell phone pics, the wear on the emulsion tubes can only be seen through a magnifier.
I will be replacing the guides, and the emulsion tubes and o rings. I am also hoping to get the emulsion tubes electroless nickel plated, I have been told this should make them last.
On a side note the needles from the Factory kit have NO wear marks, so they are made with a material that is much harder than the brass emulsion tubes. I will see if the nickel plating wears them, I have been told it won't that the nickel plating has lubricity to it and the new guides help a lot.
On the lower pic in the upper right corner of the guide you can see a small dot and a "crescent" shape, they are supposed to be on both sides and deeper, I don't know how much but several thousandths. You can feel a very slight ridge where the slide wore into the guide.
Interesting stuff Im learning!

 

[Guest]

Thought I would post some pics of the worn slide glides on the BDT38's I have. The emulsion tubes are worn out again and after only about 2000 miles… because of the guides! I would have liked to post some pics of the tubes but I don't have any way to take anything but cell phone pics, the wear on the emulsion tubes can only be seen through a magnifier.
I will be replacing the guides, and the emulsion tubes and o rings. I am also hoping to get the emulsion tubes electroless nickel plated, I have been told this should make them last.
On a side note the needles from the Factory kit have NO wear marks, so they are made with a material that is much harder than the brass emulsion tubes. I will see if the nickel plating wears them, I have been told it won't that the nickel plating has lubricity to it and the new guides help a lot.
On the lower pic in the upper right corner of the guide you can see a small dot and a "crescent" shape, they are supposed to be on both sides and deeper, I don't know how much but several thousandths. You can feel a very slight ridge where the slide wore into the guide.
Interesting stuff Im learning!

I have seen them worn all the way through.

 

[Joe H]

All the way through!! Can they even work like that???
I am noticing the problem now I can't imagine?.

The way they are now it still pulls fairly cleanly all the way through the rpm range, just can't seem to get it lean enough on the bottom or midrange and my milage has decreased noticeably. Im going to keep running it the way it is until winter. I ordered parts and they should show up soon.
I am debating electroless platting the emulsion tubes myself with a kit, have been doing some research seems easy enough. I will do an old one first to get a feel for it if I go that route.

 

[jstewart]

All the way through!! Can they even work like that???
I am noticing the problem now I can't imagine….

The way they are now it still pulls fairly cleanly all the way through the rpm range, just can't seem to get it lean enough on the bottom or midrange and my milage has decreased noticeably. Im going to keep running it the way it is until winter. I ordered parts and they should show up soon.
I am debating electroless platting the emulsion tubes myself with a kit, have been doing some research seems easy enough. I will do an old one first to get a feel for it if I go that route.

:-k Good luck Joe. The more I research these 38mm GSXR CV carbs the more convinced I am that they are a problematic application on a GS 1150. To start with they are downdraft carbs which makes float height setup critical on a side draft head. They also have design problems with premature wear of the slide guides and emulsion tubes. Joe you stated your emulsion tubes are worn out again after only 2000 miles...because of the guide wear. You are apparently going to try and resolve Suzuki's design problem on the emulsion tubes by electroless nickel plating. what are you going to do about the slide guide wear problems???

I really like CV carbs when they work properly but I just don't have the time to try and maintain and find increasingly hard to get parts for 25 year old carbs that have design flaws with premature parts wear in the carb design and are not designed for a side draft application. The guy that sold me the defective 38mm CV's on the GSXR forum finally refunded my money which covered part of the cost of a new set of Mic 36mm flat slides.

 

[Joe H]

Awesome on the refund! You will love the RS's, they work well and are easy to tune have a great sound at idle and gobs of power on top.

As I thought about how I ride now vrs then and the costs to go to RS's with jetting and filters, I will be ahead by a few hundred bucks. I don't drive it as much or as hard as I used to. So I decided to stick with the CV's because they do give much smoother around town low rpm behavior and produce good smooth power throughout the rev range because they work on air velocity and not throttle position. With good emulsion tubes and the Factroy pro kit they really work well for my driving habits and produce great power.
I bought them used with unknown milage and I put between 15 and 20 thousand on the carbs before this all started a couple years ago so they lasted awhile.

I think with Nickel plated Emulsion tubes and new slide guides and knowing the rate of wear on the guides has to do with how hard you ride, throttle changes, hard acceleration ect, and dirt, the way I ride now, and keeping my filters clean, maybe adding a foam sock over them, I should be good to go for much more than 20,000 more. Which at my current rate of riding that bike would put me past retirement age!! WOW, thats a depressing thought, I either need to ride that bike more or age less!

 

[jstewart]

Well guys I changed my mind and decided I just had to have a good set of 38mm GSXR CV's. So now I have 3 sets of carbs for my 1150 restomod project. Must be crazy but I love to experiment. First stage will be the stock carbs and air box without the lid & with K&N filter. I want to run the stock pipes and dyno my fresh 1229 to see how it likes the stock carbs, air box & pipes. I am going to show the bike with the stock look at a vintage Japanese motorcycle show here in Louisville in late September and then change the stock pipes to a new V&H header. Then I can start experimenting with the BST 38's & the 36mm mic carbs to see how each runs and is to live with in normal street riding. Plan to dyno these combinations to see how they compare to each other and to the stock intake & exhaust setup.

Awesome on the refund! You will love the RS's, they work well and are easy to tune have a great sound at idle and gobs of power on top.

As I thought about how I ride now vrs then and the costs to go to RS's with jetting and filters, I will be ahead by a few hundred bucks. I don't drive it as much or as hard as I used to. So I decided to stick with the CV's because they do give much smoother around town low rpm behavior and produce good smooth power throughout the rev range because they work on air velocity and not throttle position. With good emulsion tubes and the Factroy pro kit they really work well for my driving habits and produce great power.
I bought them used with unknown milage and I put between 15 and 20 thousand on the carbs before this all started a couple years ago so they lasted awhile.

I think with Nickel plated Emulsion tubes and new slide guides and knowing the rate of wear on the guides has to do with how hard you ride, throttle changes, hard acceleration ect, and dirt, the way I ride now, and keeping my filters clean, maybe adding a foam sock over them, I should be good to go for much more than 20,000 more. Which at my current rate of riding that bike would put me past retirement age!! WOW, thats a depressing thought, I either need to ride that bike more or age less!

 

[posplayr]

:-k Good luck Joe. The more I research these 38mm GSXR CV carbs the more convinced I am that they are a problematic application on a GS 1150. To start with they are downdraft carbs which makes float height setup critical on a side draft head. They also have design problems with premature wear of the slide guides and emulsion tubes. Joe you stated your emulsion tubes are worn out again after only 2000 miles...because of the guide wear. You are apparently going to try and resolve Suzuki's design problem on the emulsion tubes by electroless nickel plating. what are you going to do about the slide guide wear problems???

I really like CV carbs when they work properly but I just don't have the time to try and maintain and find increasingly hard to get parts for 25 year old carbs that have design flaws with premature parts wear in the carb design and are not designed for a side draft application. The guy that sold me the defective 38mm CV's on the GSXR forum finally refunded my money which covered part of the cost of a new set of Mic 36mm flat slides.

I had 5 sets , now 4, (I sold the pristine set with only 2500 miles on them) of these and even undertook the slide redesign you mentioned, creating a jig and fabricated metal inserts to stop the ceramic slides from wearing down the plastic inserts. In the end, I figured it just was not worth the hassle especially if the thing was always going to be in a state of change due to the slide wear. I can still power wheelie with the CV's. You can purchase new slides, and emulsion tubes, but without some other changes the ceramic slide will chew up the sides as they have a long history doing.

 

[jstewart]

I had 5 sets , now 4, (I sold the pristine set with only 2500 miles on them) of these and even undertook the slide redesign you mentioned, creating a jig and fabricated metal inserts to stop the ceramic slides from wearing down the plastic inserts. In the end, I figured it just was not worth the hassle especially if the thing was always going to be in a state of change due to the slide wear. I can still power wheelie with the CV's. You can purchase new slides, and emulsion tubes, but without some other changes the ceramic slide will chew up the sides as they have a long history doing.

I am well aware of the slide guide wear problem as I stated in an earlier post. I don't figure it will be that much of a problem for awhile since I do not expect to put that many miles on the bike a year (probably 1,500 or less). Most of my riding is on a FJR 1300 or my VFR 1200. Plan on ordering a spare set of slide glides just in case.

 

[posplayr]

I am well aware of the slide guide wear problem as I stated in an earlier post.

My quote from you (below) actually said that but thanks for confirming the obvious.

:-k what are you going to do about the slide guide wear problems???

The slides in the carbs I had with only 2500 miles were not bad, but just starting to show slide wear. Perhaps the question above is rhetorical, but that is what I was working on.

 

[jstewart]

Which CV carb are you using on your GS 1100? I am assuming when you say the slides on the set of carbs off the 2500 mile bike were starting to show wear you meant the slide glide inserts that the slides ride in???

Sorry for the statement (I am well aware of the slide glide problem), if you took offense. I was not being a smart ass just stating that I went ahead with the purchase of these carbs with full knowledge of the problems I face with the design. I just want to play around with them and see what I can do with them on my 1229 motor.

The best designed and performing CV carbs I have experience with were the 40mm CV's that Honda put on the 98 Blackbird. At 10 inches vacuum on a flow bench test I did they flowed 148 CFM which was more than the stock head flowed by a fair margin.

My quote from you actually said, that but thanks for confirming the obvious.



The slides in the carbs had with 2500 miles were not bad, but just starting to show slide wear. Perhaps the question above is rhetorical, but that is what I was working on.

 

[posplayr]

BS36SS

http://www.thegsresources.com/_forum/showthread.php?164565-AFR-Info&highlight=AFR+Info

 

[Joe H]

I just don't see the slide guide wear as a huge problem, I have somewhere between 15,000 and 20,000 miles on them myself with unknown milage before.
It is so dependent on riding style and filtration.
I don't know how the 36's wear. The glides are different between the 36's, 38's and 40's I think, don't know how it affect wear.
My 38's are worn and it is noticeable with fine tuning the carbs but the bike is extremely ridable and I would guess most people I know would never think they were bad. I just happen to know how good they can be. I think I could easily go another 10 or 15 thousand before it would make daily riding suffer.

Now that being said If I was looking for a tourer or a rider that I was putting 10 thousand or more a year on I wouldn't have done most of the mods I have done, and the carbs would go for sure. I just don't ride enough.

Also don't the RS wear also? I have heard they do, along with almost all flat slide carbs, is that true?? I don't know from experience only what I have heard.

Jstewart I can't wait to hear how it runs and the differences in the mods your planing.

 

[posplayr]

I just don't see the slide guide wear as a huge problem, I have somewhere between 15,000 and 20,000 miles on them myself with unknown milage before.
It is so dependent on riding style and filtration.
I don't know how the 36's wear. The glides are different between the 36's, 38's and 40's I think, don't know how it affect wear.
My 38's are worn and it is noticeable with fine tuning the carbs but the bike is extremely ridable and I would guess most people I know would never think they were bad. I just happen to know how good they can be. I think I could easily go another 10 or 15 thousand before it would make daily riding suffer.

Now that being said If I was looking for a tourer or a rider that I was putting 10 thousand or more a year on I wouldn't have done most of the mods I have done, and the carbs would go for sure. I just don't ride enough.

Also don't the RS wear also? I have heard they do, along with almost all flat slide carbs, is that true?? I don't know from experience only what I have heard.

Jstewart I can't wait to hear how it runs and the differences in the mods your planing.

I was looking for long haul; with the ceramic slide wearing deeper and deeper into the plastic insert, the needle will go deeper and deeper into the emulsion tube. You would have to keep up with the mid range tuning (needle shimming). I have a WBo2 so I could see it better than with say Plug Chops.