Author Topic: Poor running below 300 rpm  (Read 1791 times)

Offline RGP750

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Poor running below 300 rpm
« on: July 06, 2016, 09:05:06 AM »
Hi All
Took the bike out last night for a 30 mile run, it hasn't been out since last year.
I had to run with varying amount of choke for first couple of miles and below 3000 rpm very "wooly"
not complete misfire but definitely not right.
When I hit 3000 rpm ish it kicks you in the back so my guess for what it's worth
is carbs.
Idle jets gummed up over winter??? when it gets to main jet ok???
If that's what it is best way to clear it without taking the carbs off.
Any ideas welcome please.
Cheers Rich
1972 500/4
1973 CB175
1972 CB175
1959 BSA Super rocket
1927 960cc Matchless 'v' twin
1969 750 K0

Greebo

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Re: Poor running below 300 rpm
« Reply #1 on: July 06, 2016, 10:01:41 AM »
Sounds like the carbs need a good squirt of carb cleaner, hopefully that will do the trick

Offline totty

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Re: Poor running below 300 rpm
« Reply #2 on: July 06, 2016, 12:34:41 PM »
Drain the float bows, fill with redex via the fuel line, leave a few days turning over occasionally to draw a little through the jets.
I find it's worth a try before resorting to removing and stripping them, it tends to work if it hasn't been stood long, I've also stored bikes with carbs full of redex.

Offline MarkCR750

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Re: Poor running below 300 rpm
« Reply #3 on: July 06, 2016, 07:58:53 PM »
You could also try removing the air box a and squirting carb cleaner down the small brass balance pipes, may not work but it's quick so worth a try.
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Offline royhall

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Re: Poor running below 300 rpm
« Reply #4 on: July 06, 2016, 08:51:04 PM »
Great idea with the Redex, will try that at some point. Got lucky with one of mine that had the same symptoms as yours, just kept running it. As long as petrol is getting through the idle jets in some amount it usually (but not always) clears with use. Like the idea of the Redex for winter storage though, does it really work.
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Offline RGP750

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Re: Poor running below 300 rpm
« Reply #5 on: July 06, 2016, 09:54:03 PM »
Thanks for your help guys.
Redex for me as well in the Winter, great idea.
I took the carbs off tonight and blasted all of the relevant holes with carb cleaner  with jets removed and back together again so will go for a blast after work tomorrow.
Cheers Rich
1972 500/4
1973 CB175
1972 CB175
1959 BSA Super rocket
1927 960cc Matchless 'v' twin
1969 750 K0

Offline totty

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Re: Poor running below 300 rpm
« Reply #6 on: July 06, 2016, 09:56:49 PM »
Whenever I've stored a bike with redex in the carbs it's always ran fine after, but of course they might have been fine just draining them so I'll never know if it worked.

Offline Trigger

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Re: Poor running below 300 rpm
« Reply #7 on: July 06, 2016, 10:21:11 PM »
Thanks for your help guys.
Redex for me as well in the Winter, great idea.
I took the carbs off tonight and blasted all of the relevant holes with carb cleaner  with jets removed and back together again so will go for a blast after work tomorrow.
Cheers Rich

I hope you blew everything out with a airline. Did it start OK ? And do you only have a daytime MOT on the K2 ;D ;D

Offline RGP750

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Re: Poor running below 300 rpm
« Reply #8 on: July 07, 2016, 06:55:00 AM »
Yes Trigg ,All clear, yes only have daytime MOT headlight crap ;D ;D (except for Tuesday when i came home late). ::)
I'll report tonight on outcome.
1972 500/4
1973 CB175
1972 CB175
1959 BSA Super rocket
1927 960cc Matchless 'v' twin
1969 750 K0

Offline Trigger

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Re: Poor running below 300 rpm
« Reply #9 on: July 07, 2016, 07:16:17 AM »
Yes Trigg ,All clear, yes only have daytime MOT headlight crap ;D ;D (except for Tuesday when i came home late). ::)
I'll report tonight on outcome.

Home late on a Tuesday night ! It is all down hill from now on ;D ;D

Offline RGP750

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Re: Poor running below 300 rpm
« Reply #10 on: July 07, 2016, 10:04:02 AM »
need to be in bed by 9-00
1972 500/4
1973 CB175
1972 CB175
1959 BSA Super rocket
1927 960cc Matchless 'v' twin
1969 750 K0

Offline Bryanj

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Re: Poor running below 300 rpm
« Reply #11 on: July 08, 2016, 06:11:25 AM »
Now I need to be in bed by 9AM

Offline RGP750

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Re: Poor running below 300 rpm
« Reply #12 on: July 08, 2016, 06:41:42 AM »
Worth taking the carbs and doing it properly,
running better than it did before.
So redex next winter storage.
Cheers all
1972 500/4
1973 CB175
1972 CB175
1959 BSA Super rocket
1927 960cc Matchless 'v' twin
1969 750 K0

Offline RGP750

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Re: Poor running below 300 rpm
« Reply #13 on: July 08, 2016, 08:10:39 AM »
Ok Guys
Forget the above.
Took it to work this morning , still the same below 3000 rpm.
Like fuel starvation ,put on choke and it picks up.
hit 3000 I assume it's coming on to main jet.
Should I be looking somewhere else????
1972 500/4
1973 CB175
1972 CB175
1959 BSA Super rocket
1927 960cc Matchless 'v' twin
1969 750 K0

Offline UK Pete

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Re: Poor running below 300 rpm
« Reply #14 on: July 08, 2016, 01:52:16 PM »
Have you sprayed easy start round the carb rubbers while its runnung to see if your sucking in excess air rich?

 

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