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Makotosun

1973 Yamaha CT3 - starts and revs full throttle

  • Jogar
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Replied by Jogar on topic 1973 Yamaha CT3 - starts and revs full throttle

So, it’s down to about 4200 rpm, I loosened the carb bolts. 

odd thing, when I put the choke back in (or turn it off) it revs way higher. 


John
1973 Yamaha RT3
1973 Yamaha CT3
1972 Yamaha DT2
1969 Yamaha AT1
1964 Honda CT200
10 Aug 2022 13:52 #11

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Replied by Ht1kid on topic 1973 Yamaha CT3 - starts and revs full throttle

Did you check your carb slide?
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10 Aug 2022 15:25 #12

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Replied by Ht1kid on topic 1973 Yamaha CT3 - starts and revs full throttle

 .                               

The back of your carburetor should look like this
10 Aug 2022 15:38 #13

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Replied by AirborneSilva on topic 1973 Yamaha CT3 - starts and revs full throttle

With it running spray some WD40 around suspected areas, intake, cylinder base gasket and head.  If there's an air leak in those areas you'll find it.
2023 Tenere T7
1976 DT400C
1975 DT400
1981 DT175H
1972 DT2 250
1980 GT80
1972 JT2
10 Aug 2022 16:37 #14

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Replied by RT325 on topic 1973 Yamaha CT3 - starts and revs full throttle

Take The Carb OFF, & without removing the slide look through it & tell us if you see us waving the other side. Ok I'm being stupid [or am stupid] but serious also. You shouldn't see any daylight under the slide if shut right down. Check that first or ya chasing your tail in my opinion.
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11 Aug 2022 00:13 #15

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Replied by Jogar on topic 1973 Yamaha CT3 - starts and revs full throttle

It does ! It’s strange though that it runs at 4000 rpm with the choke on? Then revs up crazy but steady to like 8000 when I turn the choke off

*would it make a difference if my exhaust pipe was on? 

it’s off. 
1973 Yamaha RT3
1973 Yamaha CT3
1972 Yamaha DT2
1969 Yamaha AT1
1964 Honda CT200
Last edit: 11 Aug 2022 12:31 by Jogar. Reason: Edit
11 Aug 2022 11:55 #16

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Replied by Sneezles61 on topic 1973 Yamaha CT3 - starts and revs full throttle

No… air is getting in somewhere, hence the idea of spraying around the intake manifold and jug.. if it starts to rev… give it a moment to clear and give it a shot again…… and like RT325 states.. could be the round slide is not seating… it takes a curious mind to problem solve this issue… keep after it, you’ll find it
Sneezles61
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11 Aug 2022 13:25 #17

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Replied by Jogar on topic 1973 Yamaha CT3 - starts and revs full throttle

I’ve sprayed some carb cleaner around the intake, but haven’t had any change in idle from that. I’m perplexed
1973 Yamaha RT3
1973 Yamaha CT3
1972 Yamaha DT2
1969 Yamaha AT1
1964 Honda CT200
11 Aug 2022 13:37 #18

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Replied by RT325 on topic 1973 Yamaha CT3 - starts and revs full throttle

ok but get up a photo looking in at the slide with a mirror behind it. Like in post #13 carb pic, look in there & out the back. Shouldn't be daylight or if so how much.
11 Aug 2022 21:10 #19

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Replied by Jogar on topic 1973 Yamaha CT3 - starts and revs full throttle

Ok, so here’s where I’m at. I looked in the back, it was sitting abnormally high. So I loosened the throttle up near the hand grip to let the slide down more. 

after doing that, it idles decently normal, but I experience a bit of rev hang when I’m giving it throttle. 

John
1973 Yamaha RT3
1973 Yamaha CT3
1972 Yamaha DT2
1969 Yamaha AT1
1964 Honda CT200
13 Aug 2022 10:46 #20

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