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TOPIC: CT1 carb rebuild

CT1 carb rebuild 25 May 2019 03:25 #1

  • gw1170
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Hi, thought I'd give the CT1 carb an overhaul, new washers, O ring etc and found this on the main jet, a very thin fibrewasher under the O ring, I checked the parts schematics and no washer on the pic so is this someones bodge to put the old o ring ( the larger one on my pic ) under more sealing pressure ? I guess what im asking is shall I rebuild without it and just the new O ring (smaller) in the pic ? Thank's for any help !!!!
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CT1 carb rebuild 25 May 2019 05:41 #2

  • MarkT
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There should not be an o-ring or sealing washer on the main jet.

Where is the main jet installed? Into the main jet holder that can be removed from the float bowl? Or has someone installed the main jet into the bottom of the main nozzle (aka needle jet, aka emulsion tube) ?

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

CT1 carb rebuild 25 May 2019 07:07 #3

  • gw1170
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Sorry, my mistake, this is like you say the main nozzle/ needle jet/tube,sorry, having said that should there be the fibre washer ?

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CT1 carb rebuild 25 May 2019 07:30 #4

  • MarkT
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Your picture is of the main jet. Which can (incorrectly) be screwed into the main nozzle instead of the main jet holder in the float bowl. My concern is someone may have put your carb together wrong?

It will run okay assembled incorrectly but you won't be able to change the main jet without removing the float bowl which requires removing the carb.

Assembled incorrectly, no washer or o-ring is needed.

Assembled correctly, there is a part with an o-ring groove (Yamaha calls it a "jet setter") that threads into the bottom of the main nozzle... the o-ring seals into well in the bottom of the float bowl. That o-ring is critical. No washer is used.

The washer looks like it might belong under the float needle seat that threads into the carb body.

Can you post a picture of the parts laid out how they were assembled?
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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

CT1 carb rebuild 25 May 2019 07:50 #5

  • gw1170
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Yes, the left what came out the float bowl and the right the main needle area...
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CT1 carb rebuild 25 May 2019 07:51 #6

  • gw1170
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ps the o ring was on the float bowl side of the fibre washer

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CT1 carb rebuild 25 May 2019 07:54 #7

  • darinm
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It looks like they lost the original o-ring holder and rigged that up as a replacement. Seeing as the carbs can be so fussy, I'd be inclined to find the correct part as it's a critical one.

Then again if it was working fine (or was it?) and you're ok with it...

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1972 Yamaha CT2 175
1972 Yamaha RT2 360
1972 Suzuki TS 185 Sierra
1995 Suzuki DR 350

CT1 carb rebuild 25 May 2019 08:08 #8

  • gw1170
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it was running ok and I guess the o ring will seal between the float bowl and the needle area washer so in theory...however I could order the" jet setter" part with the groove in and put it in at a later date I guess !
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CT1 carb rebuild 25 May 2019 10:59 #9

  • Mothersbaugh
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I would do that. Order the part, and do it up right.

This should serve as a warning that the PO might have taken other, ahem, "liberties," shall we say, with replacement parts and systems that you need to be on the alert for. Or said another way, sometimes making a gasket out of a beer carton works, sometimes it doesn't...

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CT1 carb rebuild 25 May 2019 12:10 #10

  • MarkT
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Yes, someone has "re-engineered" the way the bowl seals to the main nozzle.

I would either put it back the way it was using the same parts hoping it will seal okay or simply take the main jet out of the jet holder and put it in place of the that rigged fiber washer and o-ring assembly.

The drawback of installing the main jet directly into the main nozzle is the float bowl then needs to be removed to change the main jet.... so if you're changing the jetting a lot it would not be fun.

The advantage is you bypass the whole "seal the float bowl to the main nozzle with an o-ring" set up which is infinitely more reliable...

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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