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Post by vectisitch on Jul 11, 2022 13:09:26 GMT 1
So yesterday we went out on a long ride me on my 31k. Its got mutts all round pipes, road tune and banshee coils. Standard reeds and airbox. No drilling and snorkels fitted. Carbs have been ultrasonically cleaned by me and balls out done. Main jets gone up 2 sizes to suit the pipes and standard pilots.
Problem is it seems to stutter and choke up on anything up to half throttle. If I open the throttle or it reaches 7k when the power comes on she clears and absolutely flies. The plugs are biscuit brown on the electrodes but a little black and oily around the outside. Any ideas please? Before I start stripping the carbs again. I also have 6mm reedspacers fitted? Would taking those out help?
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Post by midlifecrisisrd on Jul 11, 2022 13:33:10 GMT 1
Bin the snorkels 😆
Its rich in the midrange
If you want to keep the snorkels then try dropping the needle or going one size down on the main
Steve
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Post by jessy03 on Jul 11, 2022 15:25:14 GMT 1
If it’s tuned with pipes I’d remove both snorkels and drill both lids, up jet to 300/27.5
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Post by vectisitch on Jul 11, 2022 15:49:29 GMT 1
I've got 260 mains in it. Surely it's a pilot curcuit problem though? As it flies on full throttle?
I thought main jet only comes in at half throttle?
Anyway I'll take the snorkels out as a start because that's easy.
Thanks so far
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Post by vectisitch on Jun 13, 2023 17:37:31 GMT 1
I did drop the needle one slot which helped a lot but not perfect and rode it all last year like that. Took carbs off today to clean as the bike started bogging down a bit. Partially blocked pilot in the left carb. I took out the 260 mains and put in 250s and put the needles back to stock. Back to stuttering again at 5k to 6k. Snorkels are still in. Air screws are at 1.5 turns out.
Any ideas? Needles dropped again? Or just take the snorkels out? If I do that should I put the 260s back in? Is it worth dropping sizes on the pilots?
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Post by midlifecrisisrd on Jun 13, 2023 17:48:27 GMT 1
I'd put the 260's back in as you have proved that isn't the problem and with a bit of a tune tune and pipes I'd expect
Get the snorkels out
Steve
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Post by midlifecrisisrd on Jun 13, 2023 17:49:20 GMT 1
Oh and if you are keeping the snorkels in I'd try down on pilot 1 size
Steve
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Post by vectisitch on Jun 13, 2023 18:06:51 GMT 1
Tomorrow I'll take the snorkels out and go back to 260 mains. Leave the needles at standard?
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Post by midlifecrisisrd on Jun 13, 2023 18:09:21 GMT 1
For now yes
Steve
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Post by vectisitch on Jun 13, 2023 18:27:27 GMT 1
Thanks. I hate taking the carbs off. Pita
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Post by vectisitch on Jun 13, 2023 18:32:44 GMT 1
 Is it both the snorkels circled or just number 21? |
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Post by midlifecrisisrd on Jun 13, 2023 19:11:25 GMT 1
Usually both 😬
Steve
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Post by vectisitch on Jun 14, 2023 17:28:44 GMT 1
Well I took both out and put 260 mains back in. The bike starts up and ticks over at 2k/2.5k and stays there. Revs drop very slowly. Tickover screws make no difference at all. I wound the airscrews right in and that also made no difference
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Post by jessy03 on Jun 14, 2023 17:52:04 GMT 1
My set up was similar to yours, I was on 290/27.5, gutted airbox (drilled lid and tray, both snorkels out)
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Post by midlifecrisisrd on Jun 14, 2023 18:43:53 GMT 1
You sure you don't have an air leak somewhere?
Did you put the choke link pipe back on
Only suggesting as revs are hanging
Steve
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Post by vectisitch on Jun 14, 2023 18:59:04 GMT 1
Choke link pipe is on. I'm taking everything back off and redoing it. Something isn't right
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Post by LC_BOTT on Jun 14, 2023 19:12:42 GMT 1
Thanks. I hate taking the carbs off. Pita Do you have to take them off? I remove the tops/slides and link pipe, then just spin them round in the rubbers. |
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Post by vectisitch on Jun 14, 2023 20:09:23 GMT 1
Thanks. I hate taking the carbs off. Pita Do you have to take them off? I remove the tops/slides and link pipe, then just spin them round in the rubbers. I find it a pita getting the link pipe back on. Just seems fiddly as hell working on pv carbs |
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Post by Tobyjugs on Jun 14, 2023 20:57:44 GMT 1
Well I took both out and put 260 mains back in. The bike starts up and ticks over at 2k/2.5k and stays there. Revs drop very slowly. Tickover screws make no difference at all. I wound the airscrews right in and that also made no difference Sounds to me like its too rich on pilots. Symptoms for this is higher than normal idle and when warm the idle speed drops or doesnt idle. If you turned the air screw 2.5 to 3 turns out and it idled fster i would drop down one size on the pilots. |
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Post by oldbritguy on Jun 14, 2023 21:40:23 GMT 1
Make sure vacuum pipe for fuel tap is securely fitted.
I had similar issue some time back with revs taking ages to drop and no adjustment made any difference. Pipe was split at the carb spigot.
Regarding the rich running I always start from standard settings and work up and down from there (jets/needle positions etc) with lots of plug chops
John
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Post by vectisitch on Jun 14, 2023 22:29:11 GMT 1
Well I took both out and put 260 mains back in. The bike starts up and ticks over at 2k/2.5k and stays there. Revs drop very slowly. Tickover screws make no difference at all. I wound the airscrews right in and that also made no difference Sounds to me like its too rich on pilots. Symptoms for this is higher than normal idle and when warm the idle speed drops or doesnt idle. If you turned the air screw 2.5 to 3 turns out and it idled fster i would drop down one size on the pilots. Pilots are standard 22.5 |
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Post by vectisitch on Jun 14, 2023 22:30:35 GMT 1
Make sure vacuum pipe for fuel tap is securely fitted. I had similar issue some time back with revs taking ages to drop and no adjustment made any difference. Pipe was split at the carb spigot. Regarding the rich running I always start from standard settings and work up and down from there (jets/needle positions etc) with lots of plug chops John While I've got it all off again tomorrow I'm going to replace the vacuum pipe and the choke balance pipe although they do look OK to me |
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Post by KevtheRev on Jun 15, 2023 9:52:10 GMT 1
I'd try it on standard jetting before I'd go drilling or changing anything .
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Post by vectisitch on Jun 15, 2023 12:12:54 GMT 1
I'd try it on standard jetting before I'd go drilling or changing anything . Not drilling anything. Engine is fast road tuned with skimmed head. Mutts all round pipes so standard jets won't work. It makes sense to take the snorkels out. But I suspect 260 mains will probably be too small after that |
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Post by abar121 on Jun 15, 2023 12:59:56 GMT 1
Something still isn't right. I would strip the carbs right down and put them in an ultrasonic cleaner. Then blow through everything with an airline / carb cleaner.
Pressure test the motor and check all the lines including fuel, then stator, coils, wiring etc.
I don't get how it would be apparently so rich in the midrange with stock carbs with a stock airbox, even with pipes / moderate tune.
I had a similar problem, but that was with PWKs, a different kettle of fish entirely.
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Post by stusco on Jun 15, 2023 13:04:43 GMT 1
Nothing to do with your problem but what is your squish with your skimmed head ?
I melted a piston because my compression was to high☹️ ,bike was fast though 😁for a while anyway
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Post by vectisitch on Jun 15, 2023 14:29:57 GMT 1
All back together and running OK. Ticking over well. I had obviously done something wrong. Any way after a road test it feels like it's still got the quarter throttle stutter between 5 and 6k revs after that it feels faster but that's because its now very lean. Squish is 1mm. After a plug chop  So I'm now thinking I'll put the bottom snorkel back and drop the needle one notch. |
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Post by stusco on Jun 15, 2023 15:41:56 GMT 1
1mm sqiush is the minimum im sure you know that, dont go putting crap fuel in it
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Post by vectisitch on Jun 15, 2023 16:00:55 GMT 1
1mm sqiush is the minimum im sure you know that, dont go putting crap fuel in it Only use Esso 99 octane. No Ethanol supposedly |
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Post by vectisitch on Jun 15, 2023 17:56:02 GMT 1
Ok so it's all back as it was. 22.5 pilots 260 mains with needles dropped 1 notch. Snorkels are back in. It's not far off being perfect. Pilot blocked must have been causing the bogging down. Very slight stuttering at 5 to 5k but only on small throttle opening. Open it up and it clears. Without dynoing it I think that's as best as I can get it. She flies.
Who needs a powerband when you have afterburners? 😆
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