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BS34 poor idle on hat start. 13 Sep 2020 09:32 #834918

  • VTEC
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Sorry. Hot start.

Playing around and put the OEM carbs on with the air box. Runs good, but on a hot re-start it will barely idle. Starts at like 200 rpm, sometimes have to crack the throttle to get it going. Then after running for several seconds it climbs up to normal idle speed and everything is fine. Screws are at 2 1/4 turns out, and air/fuel meter is showing 13:1 when idling normal. During the hot start problem it's showing lean.
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Last edit: by VTEC.

BS34 poor idle on hat start. 13 Sep 2020 12:14 #834920

  • TexasKZ
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Have you checked the fuel level in each carb?
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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BS34 poor idle on hat start. 13 Sep 2020 13:40 #834932

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TexasKZ wrote: Have you checked the fuel level in each carb?


Yes, confirmed with ruler and fuel hose.

Jets are clean. Wondering if I have a pilot passage plugged up?

The cold start enrichment helps hot start?
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Last edit: by VTEC.

BS34 poor idle on hat start. 13 Sep 2020 15:04 #834943

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Could be a clogged pilot circuit, though it seems like it would stay clogged hot or cold.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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BS34 poor idle on hat start. 13 Sep 2020 15:53 #834946

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TexasKZ wrote: Could be a clogged pilot circuit, though it seems like it would stay clogged hot or cold.


Maybe it's just having a bigger effect hot. I'll tear them down and check them all. Originally carb #2 overflowed when I opened the gas valve. Cleaned the float needle and seat it it's seems ok now.
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BS34 poor idle on hat start. 13 Sep 2020 16:21 #834948

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How has your engine top end been upgraded?
What carbs were you running before switching to the BS34's?
1982 KZ1100-A2

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BS34 poor idle on hat start. 13 Sep 2020 17:26 #834954

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daveo wrote: How has your engine top end been upgraded?
What carbs were you running before switching to the BS34's?


10.5:1, APE street porting and 410 cams. Also have FCR35s, and this problem doesn't happen with them.
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BS34 poor idle on hat start. 13 Sep 2020 18:05 #834955

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Almost seems like a hot soak condition. Shut down hot engine, gets hotter from stopping air and fuel flow, fuel boils in the carbs. Never heard of that on a bike though.
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Last edit: by VTEC.

BS34 poor idle on hat start. 13 Sep 2020 19:32 #834957

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What pilot and main jets?

I'm no expert, but my guess is the BS carbs are jetted way too lean for the engine setup, and the air box is significantly restricting air flow.
Kinda like wearing a stupid Covid mask while working your a$$ off.

:sick:
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BS34 poor idle on hat start. 14 Sep 2020 10:25 #834990

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I think I got it. The choke levers are all bent keeping the plungers in the wrong positions.

And the #2 carb is wrong. Doesn't have the ball and spring for the choke rod detent.
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Last edit: by VTEC.

BS34 poor idle on hat start. 16 Sep 2020 15:21 #835185

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Fixing the choke took care of half the problem. I think the other half is fuel boil. Going super rich on idle mixture seems to fix that. Read in another topic like high 11s afr at idle works best.
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BS34 poor idle on hat start. 17 Sep 2020 07:29 #835217

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I'm thinking about putting the idle mixture back where it should be, and run it on non-ethanol gas from Home Depot. This would prove the issue is with the lower boiling point of the the gas with ethanol.

I'm also gonna check temperatures after a hot shutdown to see which is hotter, the carb bowls, lines, or fuel valve? I have a chrome Pingle valve which is close to the head.

Has anyone else been having heat soak issues? I know it's been an issue for awhile. Especially when they're still pumping winter blend fuel in the hotter months.
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