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TOPIC: Carb questions

Carb questions 09 Jan 2019 16:19 #1

  • Lucas de los Rios
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Hello everyone,

So I'm working with a 71 RT1B. Have to replace the carb due to damage from PO. I have ordered a replacement vm32 as I couldnt find a vm32sh. Not even sure what the sh means.

Question 1 to you guys is what is the bolt hole center to center?

I am ordering parts but won't be with my bike for a while. The vm32 I ordered is spigot not flanged since I couldn't seem to find one flanged, so I need to order a flange and have several options for bolt position.

It appears the original carb has a starter jet and no air jet. The new carb I order has an air jet but no started jet.

Question 2 is this a problem or will it be perfectly compatible?

Already plan on adjusting jetting from new carb.

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Re:Carb questions 09 Jan 2019 16:36 #2

  • Lucas de los Rios
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Here are the new carb specs vs old

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Re:Carb questions 09 Jan 2019 18:57 #3

  • RT325
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It'll be good with a rubber flange to mount it. 200 main might be a bit lean but 'i think' slide needle restriction determine's the main jet size to some extent. Original carb i see on Partzilla is a 220 main but that had a side mounted main jet externally accessed in the bowl so not sure how closely original jet sizes equate but would be somewhat relevant for sure. your new carb will have a starter jet even if not mentioned which is a drilling in the cavity in the bowl, a small brass fixed jet down the hole. Original carb had to get its air from somewhere so probably just never mentioned it if can't be replaced. Actually i'm talking rubbish, the air jet will be straight into the slide needle jet looking in the mouth of the carb. Choke air is just a big drilling leading to the choke piston in the carb mouth. Air to the needle jet--emulsion tube-- in the original carb is possibly metered by the air hole at the needle jet itself, so not mentioned as such. Talking choke, i hope you've 'not' bought a carb off a twin twostroke & this one has no choke. I bought a snowmobile carb once & was from a twin with the choke on the other carb & piped across like a Yamy RD 350 twin, so my bad luck. Don't think you'll be that unlucky. Someone will be along with more sensible advice lol or probably already have seeing i'm a slow typer. I've got a 36mm on my RT2 Rat Bike but no idea on jetting now. Cheers.

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Re:Carb questions 09 Jan 2019 20:05 #4

  • asco
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These vintage bikes run best with the correct carburetor. I would have searched out a used carburetor or purchased parts for the original carburetor. Too many variables and lean conditions based on aftermarket exceeds standard replacement.

Welcome to vintage YE-ENDUROS !

a

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Re:Carb questions 11 Jan 2019 02:18 #5

  • Davesspeed
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The most important thing is the higher throttle fuel curve. You can install the main jet, emulsion tube, and slide needle from the original carb into the new carb, or look up what the original ones were and order those parts. The slide cutout number affects part throttle response only. The higher the #, the leaner it is. You just have to try it, if it doesn't take throttle well from an idle, and the idle is good, then go smaller. I think 2.5 is more common. Again, if you have the original slide, you might be able to install it in your new carb too.

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Re:Carb questions 11 Jan 2019 07:11 #6

  • Lucas de los Rios
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Thanks for the replies.

I was planning on moving all salvageable parts to the new carb.

I think my jets, tube and needle are good but unsure if the wear on the valve is ok. There's no raised surface or cuts. Just smooth wear at the top and bottom.

What do you guys think?

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Re:Carb questions 11 Jan 2019 10:39 #7

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That's kinda wierd that the wear pattern is so short, almost like it is a size smaller on the bore and is riding cocked in the bore. Either that or your getting a lot of debris from the top. If the slide fits snug in the bore than it looks fine to me. Really not much wear on the sides of it.

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