Honda-SOHC
SOHC.co.uk Forums => Other Bikes => Topic started by: yozzer74 on June 20, 2018, 08:33:01 PM
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Hi long shot this question. My gs550 is running really bad I've fitted k&n pod filters custom 4 into 2 pipe .Bike as c.v carbs dyno jet stage 3 kit fitted .problem is bike ticks over nice first part of throttle is good .When stood revs all way to red line .but when under load doesn't want to rev and pops and bangs bogs down .I've tried lifting needles up bigger main jets but makes no difference at all.im thinking it could be a timing issues. Anyone got any ideas I'm a little stuck .Cheers yozzzer
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You could try a "quick and dirty " test by wrapping the pods with a towel or fleece around them to see if it changes at all, and if it does then better or worse.?
Popping and banging sounds like weak mixture initially. Timing, have you confirmed with a strobe if it's advancing as it should?
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K2 tried covering the filters didn't make any difference .but when I covered them up about 80% was worse .I've not checked with timing light I've got one on order .it does have electronic ignition with a ignitor box .bike is a 1982 model
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check the plug gap,
I had popping with a lean mixture
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Plug gap ok I should have said when I had it on dyno the technician said I had other issues other than carbs as it is only making 27bhp should have around 47bhp .I did a compression test and results were from 140psi to 150psi.
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Generally with electronic ignition they either go or stop so hopefully it'll check out ok. But it would be good to confirm it else you could be chasing your tail unnecessarily.
I don't know how much you know of the carbs or how they work? The throttle butterfly is opened by the twist grip but the main slide is pulled up with a vacuum so has some means of sealing to get the vac to lift the slides, often a rubber diaphragm. Have you checked anything relating to this area to make sure you've not got any impairments?
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K2 the carbs have been totally overhauled. And I agree with you that the ignition works or doesn't work .the bike also has new dyna coils fitted .And has a a nice blue spark .
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I can see why you're puzzled by it, doesn't seem to make sense.
Static with no load it should get to red line with something like one third throttle opening so you are not using much carb range to do that. It suggests the ignition is advancing also.
A bit left field but, could you do a run out with the pods removed and something like a go-pro looking at the carb slides to see what they are doing? They should be rising as a match to the engine revs as air volume increases and drop shut when you close the throttles. They shouldn't flip straight open as you apply throttle as it'll screw the jetting.
Has cam timing been worked on at all?
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Did it run right with standard air box and filter, pods and CV's don't mix you either get top end or bottom, never perfect due to disruptive air flow.
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I’ll second the disruptive airflow theory, try it with the standard airbox if you can, or fit velocity stacks, long ones if you can get them.
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Well got the bike running a lot better now when I took the cam cover off found the cams out of time by one link .bike also had a head gasket leak so I did that at same time had head skimmed valve seats recut along with valves and all valve gaps set .only a few shims needed .still getting a little poping from carbs on first part of throttle when it's on pilot jets .air mixture screw is now 31/2 turns out which made it a lot better .so still a little work to do to get it bang on .
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Pic of bike [attachimg=1]
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Hi Yozzer.
Good to hear your making progress. I’m running a 78 GS 1000 and found this forum to be invaluable for all thing GS, https://www.thegsresources.com (https://www.thegsresources.com) . Hope it helps, nice bike by the way.
Cheers,
Greg
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Slowly sorting out the issues then. Sounds like progress at least.
Bike looks good.
You could try raising the fuel level by changing the float settings to see if you can just bring the mixture up a bit at the bottom end of carb opening and see if you get a more normal airscrew position.
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Nice bike Yozzer - whats it ride like on the 'knobblies'?
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Philward it rides surprisingly good .bit bumpy at low speed but ok when speed picks up.k2 I was going to try bigger pilot jets ? Do you think floats position will work
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This link come from the GS Resources forum and is an invaluable guide to adjusting carbs. Hope it helps.
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html
All the best,
Greg
Edited to get the link working.
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Philward it rides surprisingly good .bit bumpy at low speed but ok when speed picks up.k2 I was going to try bigger pilot jets ? Do you think floats position will work
It'll affect the lowest speed mixture more than the rest of the range but it's a real "suck it and see" to judge how much it can influence it.
Ultimately it appears to need just a little more fuel metered to clean up that low speed response (verified by the improvements you get with the screw setting) so whichever is convenient to change first is worth trying.