jsmith1107
XS650 Addict
Does it matter what year bowls I put on as long as they fit? This set does not have the overflow--does that matter on the year carbs I have?
-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
These fit my carbs but any issue if not same year?
- Thread starter jsmith1107
- Start date
Does it matter what year bowls I put on as long as they fit? This set does not have the overflow--does that matter on the year carbs I have?
Maybe,maybe not. They may bolt together and if so can be made to work. Carb tuning can be a bit more frustrating though.
Pilot jets get air flow from ports in the carb bell to mix with the fuel then send it on it's way. Some years use a jet that mixes air from the top, others from the bottom.
Thought I had some pics showing these differences in the float bowls. Can't seem to find them. Ought to get my pics better organized.
I had a set of 76/77 carbs with earlier float bowls on them. They drove me crazy trying to tune them. The earlier carbs used one type of set up the later the other. Once I realized this and altered my procedures to match then things worked ok.
The earlier had the air mixing before the pilot get metered it so the jets need to be larger. In the mid 40's sizes. The later metered the fuel then mixed it. These used jets in the mid 20's range. When trying to use one jet in the other bowls things don't work.
You need to know which bowls those are and use the right jets.
Once I figured that out my bike did ok.
On those bowls you see a passage that runs across the top of the pilot jet. It comes down from the top turns to the right about 45* when it crosses the jet and goes down and turns down again. This bowl uses jets that mix air after metering the fuel. Fuel flows up from the float bowl through the jet and mixes wirth air in that passage then goes onto where it comes out ports by the throttle plate.
This set up was used on the 76 to 79 carb sets. They used jets in the mid 20's range.
The earlier float bowls had a hole drilled from where that passage turns down below the jet at an angle so it allowed air to flow down to fix with fuel before it passes through the jet. These jets needed to be larger to pass the mixture. Thus jets in the mid 40's range.
As I mentioned this won't be a real problem as long as you realize this and alter your tuning to match. The next owner may find it fun to figure out though. Then you get to be the dreaded PO.
Leo
Pilot jets get air flow from ports in the carb bell to mix with the fuel then send it on it's way. Some years use a jet that mixes air from the top, others from the bottom.
Thought I had some pics showing these differences in the float bowls. Can't seem to find them. Ought to get my pics better organized.
I had a set of 76/77 carbs with earlier float bowls on them. They drove me crazy trying to tune them. The earlier carbs used one type of set up the later the other. Once I realized this and altered my procedures to match then things worked ok.
The earlier had the air mixing before the pilot get metered it so the jets need to be larger. In the mid 40's sizes. The later metered the fuel then mixed it. These used jets in the mid 20's range. When trying to use one jet in the other bowls things don't work.
You need to know which bowls those are and use the right jets.
Once I figured that out my bike did ok.
On those bowls you see a passage that runs across the top of the pilot jet. It comes down from the top turns to the right about 45* when it crosses the jet and goes down and turns down again. This bowl uses jets that mix air after metering the fuel. Fuel flows up from the float bowl through the jet and mixes wirth air in that passage then goes onto where it comes out ports by the throttle plate.
This set up was used on the 76 to 79 carb sets. They used jets in the mid 20's range.
The earlier float bowls had a hole drilled from where that passage turns down below the jet at an angle so it allowed air to flow down to fix with fuel before it passes through the jet. These jets needed to be larger to pass the mixture. Thus jets in the mid 40's range.
As I mentioned this won't be a real problem as long as you realize this and alter your tuning to match. The next owner may find it fun to figure out though. Then you get to be the dreaded PO.
Leo
jsmith1107
XS650 Addict
I think you are talking about this bowl--on the inside it's drilled down at a 45 degree angle like you mentioned.
This is why it's very important to positively identify the year of the carb set you're working with. Many carb parts will physically swap but may not work correctly. The float bowls are a perfect example. Two different pilot jet types were used in the BS38s during their production run and the float bowls differ internally for each. Basically, the BS30/96 type pilot was used up through 1975, the VM22/210 type pilot from '76 to '79. The main difference in the bowls was, as Leo mentioned, how the air was fed to the jet .....
The first bowl you showed without the overflow pipe is from a '78-'79 carb set. It will work (with the proper jet size and type) on any '76-'79 carb. The overflow pipe was eliminated in '78 when Yamaha changed to the vacuum petcocks. I guess they figured the carbs would never overflow with those "better" petcocks. 30+ years later, that isn't always true, lol.
The first bowl you showed without the overflow pipe is from a '78-'79 carb set. It will work (with the proper jet size and type) on any '76-'79 carb. The overflow pipe was eliminated in '78 when Yamaha changed to the vacuum petcocks. I guess they figured the carbs would never overflow with those "better" petcocks. 30+ years later, that isn't always true, lol.
jsmith1107
XS650 Addict
Yes, the only difference between the bowl above and the ones you bought is the overflow pipe. Both are VM22/210 type pilot jet bowls. To I.D. the type of pilot jet you have, you must look in the ends. The two types look very similar and will physically interchange, but they flow differently because the metering orifice is on opposite ends .....
I can't really recommend a size because you haven't given the year of your carb set. When you replace jets, or change to larger ones for mods, you base those changes on the year of the carb set, what was stock in that set, not the year of the bike. Here's a chart showing what was stock for the various years. As you can see, the specs changed like every couple years .....
I can't really recommend a size because you haven't given the year of your carb set. When you replace jets, or change to larger ones for mods, you base those changes on the year of the carb set, what was stock in that set, not the year of the bike. Here's a chart showing what was stock for the various years. As you can see, the specs changed like every couple years .....
jsmith1107
XS650 Addict
Ok, I see what you mean now. I bought this bike after it was disassembled so I am not even sure the carbs are correct for it. The bike is titled as a 76. I know on the intake side of the carb, it has an M on it. Is that how I know the year of the carb itself?
jsmith1107
XS650 Addict
That is a '76-'77 set. There are several "tells". First, it's a linked set, or a "bank". '75 and older sets were two separate carbs not tied together by brackets. Next, the float bowls have overflow nipples. Last, the intake bell, besides the oval slot at the top, only has 2 round holes along the edge. The later '78-'79 set had 4 .....
76 - 77
