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BST38s hanging revs


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On 6/24/2022 at 9:26 AM, Captain Chaos said:

I'm having the same problem now with my B12 engine and carbs. Roll off the throttle, revs drop slowly. Snap it shut, all ok. With warm engine only. Had been OK for years but a few weeks ago this problem appeared.

Tried new spark plugs, a new throttle cable, no difference. Tried without throttle cable, no difference. Ultrasonic cleaned the carbs and reassembled carefully, no difference.

Now going to adjust the valve clearances (weather permitting, it's too nice to work on the bike, better go for a ride on one of the other bikes :D) and see what difference it makes.

 

 

Inlet runner orings would be my first point of call . Spay brake cleaner between the rubbers and head while on tick over to see if revs rise . If do you need new o rings 

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On 6/24/2022 at 4:26 AM, Captain Chaos said:

I'm having the same problem now with my B12 engine and carbs. Roll off the throttle, revs drop slowly. Snap it shut, all ok. With warm engine only. Had been OK for years but a few weeks ago this problem appeared.

Tried new spark plugs, a new throttle cable, no difference. Tried without throttle cable, no difference. Ultrasonic cleaned the carbs and reassembled carefully, no difference.

Now going to adjust the valve clearances (weather permitting, it's too nice to work on the bike, better go for a ride on one of the other bikes :D) and see what difference it makes.

 

 

Capn'....check for wear on the slide needles 

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1 hour ago, no class said:

Capn'....check for wear on the slide needles 

yes the needles are worn. The hanging revs problem appeared suddenly, not gradually which would be logical with wearing needles.

The last two weeks the bike has run pretty much ok. Went to work on it a few times (20km each way), last week it was f*cking hot here, 35 deg. C in the afternoon. This week was around 25 deg., "normal" summer weather, and it runs slightly better.

Yesterday however when I came home the idle had mysteriously gone up to around 1800 rpm. Tacho starts showing from 3000 rpm so not sure exactly how much, but definitely higher than before. Going to fire it up tomorrow, and see how it behaves. Took the Desmomobile to work today so the Suzuki had some rest.

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On 7/8/2022 at 4:49 PM, Captain Chaos said:

Going to fire it up tomorrow, and see how it behaves.

Fired it up, went for a ride (55km) and all seems to be OK. Idle is normal again although I did not adjust it. According to a mate riding behind me there's no smoke coming out of the exhaust, it smells slightly rich under acceleration.

Weather was the same, 25 degrees, dry, windy.

 

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  • 2 weeks later...

Did a nice long ride today, weather was up around 30, still getting what I’m guessing is heat soak in the carbs. After awhile of sitting in slowish traffic, revs still hang up around 4-6K. Below that they close normally, and if I took it up to 8-9K, they acted normal. Thinking about just ordering up new emulsion tubes from dynojet and seeing how they react. The weather is too nice to pull the bike off the road for very long right now. 
 

Otherwise they still feel pretty good. Going through the mountains I had it up to around 130MPH, power was starting to fall off a little, but I think we were up around 4K feet. 

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On 7/10/2022 at 7:15 PM, Captain Chaos said:

According to a mate riding behind me there's no smoke coming out of the exhaust, it smells slightly rich under acceleration.

My mate must be blind.

Last week we went for a ride, eat pizza in a town 90km away,  and swapped bikes, he on the B12/EFE and me on his GSX1400. I could clearly see the black smoke on WFO throttle and higher revs.

So I ordered new float needles, picked them up today, will replace them when health allows (now I have holidays, the weather is good, but I have the flu)(no corona thank f*ck) and see from there.

By the way, a stock GSX1400 is an overweight underpowered piece of shit.

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3 hours ago, Captain Chaos said:

 

By the way, a stock GSX1400 is an overweight underpowered piece of shit.

Could have told you that xD

Nothing a new exhaust + cams can't fix. That combo gets you 130hp and 130Nm.

Still not what you expect from 1402cc

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2 hours ago, Blubber said:

Could have told you that xD

I knew that already. When they were new (20 years ago..... shit time flies) i maintained a couple of 1400s when i worked for a Suzuki dealer. Of course i test rode them, so i knew what they were like. 
Last weeks ride only confirmed it. 
 

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