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Hit pothole....now it doesn't idle

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23 Apr 2022 19:51 #866031 by Dan77kz750
Hit pothole....now it doesn't idle was created by Dan77kz750
1977 kz750b twin. Stock carbs, stock airbox, good condition rubbers etc. 

Was riding today all day. Bike was running. beautifully. Not far from home a car almost merged into me, forcing me to swerve and this gigantic pothole was unavoidable. 

Hit so hard the tailight lens broke off the bike, rear shocks bottomed out and damaged the remote shock resevoirs, no other obvious damage. 

Immediately pulled over to check and the bike idled ok while I assessed the damage.  A few blocks closer to home it wouldnt stay running without some throttle. Decent amount of exhaust popping when revving the bike. Idle was inconsistent.

Im gonna start in the morning by setting my idle speed and pilots to stock as a fresh baseline, any ideas what else to look at or why a hard hit like this would mess with my carbs?

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23 Apr 2022 19:58 #866032 by azman857
Replied by azman857 on topic Hit pothole....now it doesn't idle
Pipes  flattened under the bike perhaps?

I don't have a plan and I'm sticken' to it! '77 KZ 650 / 750 GPz custom project in progress

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23 Apr 2022 20:14 #866034 by Dan77kz750
Replied by Dan77kz750 on topic Hit pothole....now it doesn't idle
Exhaust pipes appear to be undamaged, I will be checking them in the morning for any loose connections

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23 Apr 2022 22:51 #866040 by Ojisan rider
Replied by Ojisan rider on topic Hit pothole....now it doesn't idle
Exhaust popping is usually timing issue or lean exhaust. If lean, popping is usually when you close the throttle. On cars with distributor, if you install distributor, say 2 tooth off, it'll pop. One tooth off usually rough idle.

Hope this helps in some way.

82' KZ750-R1 cafe racer style. Clip-on, Rear set, Fork-Brace, Mikuni Flat-slide (forgot the size), Kerker.
84' GPz750 (basket case). everything are in pieces.
89' ZX750-H1 (ZX-7 Ninja). Resurrection project are on going with my KZ750. Everything is stock.

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24 Apr 2022 00:56 - 24 Apr 2022 00:56 #866043 by Wookie58
Replied by Wookie58 on topic Hit pothole....now it doesn't idle
It sounds like you have unmetered air getting in between the carbs and engine. Given the violence of the impact had it displaced the carbs in the inlet rubbers ? Or has a vacuum pipe come off?
Last edit: 24 Apr 2022 00:56 by Wookie58.

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24 Apr 2022 06:24 #866048 by TexasKZ
Replied by TexasKZ on topic Hit pothole....now it doesn't idle
Might be some rust or other crud in the fuel system got knocked loose and is partially clogging the carbs.

1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

www.kzrider.com/11-projects/620336-anoth...uild-thread?start=24

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24 Apr 2022 06:45 #866051 by Dan77kz750
Replied by Dan77kz750 on topic Hit pothole....now it doesn't idle
After checking all the obvious, it seems like the carbs are flooding. I'm gonna guess the most likely cause is crud knocked loose from the impact and clogging some carb jets or stuck float. 

I've managed to get it to a point where it will idle, not that well but it does hold an idle. Seems to idle high for a few seconds at a stop then idles down to around 1k. 

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24 Apr 2022 06:48 #866052 by TexasKZ
Replied by TexasKZ on topic Hit pothole....now it doesn't idle
You might try draining the carbs into a clean container and looking for any silt, rocks or pterodactyl bones.

1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

www.kzrider.com/11-projects/620336-anoth...uild-thread?start=24

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25 Apr 2022 06:15 #866103 by Dan77kz750
Replied by Dan77kz750 on topic Hit pothole....now it doesn't idle
For a conclusion to this problem. I got it running enough to head out and enjoy the rare 80* ohio sprong day. Carb was flooding at low speed or idle, was manageable. 

I drained the carbs this morning just using the bowl drain, flushed them by just running fuel through them, one or two extremely small flecks of rust came out of the left side carb only. Somehow small enough to get past my filters, guess I will look for smaller micron filters. (Not unexpected, my tank was rusty as can be last season when I bought it, even though I evapo-rusted it last fall I'm sure there are still tiny particles stuck places) 

That all said.......bike runs great now with just that simple fix. Idles better than it did before the pothole. Gonna road test some this morning before it rains but I think it's fixed. 

Thanks everyone, always appreciate how responsive this group is. 

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25 Apr 2022 08:58 #866109 by Mikaw
Replied by Mikaw on topic Hit pothole....now it doesn't idle

Pipes  flattened under the bike perhaps?
This was a great guess. I wouldn’t of thought of asking it. Makes great sense. 

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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25 Apr 2022 11:22 #866117 by F64
Replied by F64 on topic Hit pothole....now it doesn't idle
Research the ideal filter size. Gravity feeds don't like too tight of a filter. I looked it up awhile back I just can't remember the micron size.

81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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25 Apr 2022 14:56 - 25 Apr 2022 14:57 #866130 by TexasKZ
Replied by TexasKZ on topic Hit pothole....now it doesn't idle
These filter down to 10 microns and have a washable filter media, so it basically never needs replacing. I have one on my ZRX and have been pleased as punch with it.

golanproducts.com/product-category/filters/super-mini-filters/

1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

www.kzrider.com/11-projects/620336-anoth...uild-thread?start=24
Last edit: 25 Apr 2022 14:57 by TexasKZ.

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