Are all the plugs the same colour, and have you confirmed a good spark across the set?
Today is chop test day. Confirmed good sparks.
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Did you set the carb floaters height?
If not done properly, the engine won’t have enough gas
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Yes thanks I did.
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Thank you. To all.
So busy day.
Checked the carbs over, found main jet O rings were perished so changed them.
Put in 115 main jets
Tweaked the Ignition timing, a little.
Removed the inline filter.
Reset the carbs by ear.
Compression is good.
Then started doing trial runs.
1/ Over all not much improvements and still having problems reaching top end.
So
2/ Did a run without baffle, ( wow loud or what), seemed freer no real difference.
3/ Removed air filter box side,********** YES that’s the solution, massive improvement.*********
4/ Put baffle back in, no real difference.
5/ Took out the Air Filter, then put side of box back on, back to poor response.
6/ Baffle in Air box sides off = 100mph. ( Private road.)
The problem seems to be Lack Of Air.
What now?
Drill holes in the Air Box?
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Fuck the airbox off out of it. Put on some bellmouths… 
it’ll look good, taste good and, by golly, do you good…over… 
, thankyou, welcome…
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If a patient is suffering a restrictive airway, we do all we can to open the airway and let them live!
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I have been advised that it may be, my float heights are too high, cutting off holes in the emulsion tube and making my mixture too rich. Too much fuel needs more air, so works better when the airbox is open. Seems to make sense.
What do you think folks?
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Sounds reasonable, the four into one will have some effect too though not more than a single main jet increase.
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A plug chop should show richness and cost money for the sawn up plugs. Although I think the jury is out for whether this now still actually works for the (make money for Sherman farmers) ethanol fuel.
Measure the float height and adjust - have a look on here, they seem to know about these machines
https://thegsresources.com/
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Thanks Iron, Yes they are a great resource, Specialised and accurate.
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This morning I checked the float height, which was correct. I checked the plugs which were very sooty, so figured even with the Airbox side opened it was too rich. So I cleaned the plugs, reset the air/fuel screws and replaced the 115, ( V and H recommended main jet size), with standard (?) 102.5 main jets.
Trial run with the Airbox open showed great acceleration and easily exceeded 100mph, on a private road, so I was very pleased. I replaced the Airbox side and set off again fully expecting a poorer performance this time.
Fantastic result even more responsive if anything, revved right through the range quickly and easily, I backed off at 105mph in 4th.
I will still have some fine tuning to do, no doubt.
Thank you all. Although some opinions have been divided, all have been useful, and I am grateful for all the advice and information. Ride on.
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About feckin time 
Hehehe. Keeps me out of trouble.
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At those speeds on the … AHEM … “private road” I’m thinking it actually might not be keeping you out of trouble!! 
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I have been and done around 400 miles on the Suzuki and been having a good time doing them. One problem is I was using too much oil, I would say around 50ml every 70 miles.
I found that the cam chain tensioner was leaking. It has two o rings and a seal so I replaced them and cut my oil leak in 1/2. She never leaves a trace, ( on the floor) but always uses. So I wanted to make sure it wasn’t burning it all. I found she was leaking from the clutch push rod seal and the gear change indicator o ring.
The push rod seal is a strange seal 47mm diameter 8mm hole and 8mm thick. I could not find anything like it even in the oil seal/ bearing suppliers for industry never mind a legit Suzuki part.
After searching pages of google and finding “not in stock” everywher,e I found two sites in Holland. the seal wasn’t cheap ether, I thought I would buy both cos they were so rare, and have a spare, I could sell if it wasn’t needed.
One arrived and the other didn’t.
After checking Trustpilot I saw why, this guy just lets you buy stuff, and then you never hear from him again, cant contact him anyway you try, watch out people, " oemmotoparts" also trading as “goparts”. Don’t do business with them.
Paypal refunded me very quickly.
Got the part fitted 2 days ago and seems good It will have to wait till Sunday for a test. These old bikes, the seals, tyres o rings are all knackered, Ive learned.
Got some second hand shiny cam caps too.
P.S. I will straighten the tail section this winter.
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Did you get the milf on line?
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Suzi is looking fine!!!
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Never ending?
24,000. miles, original pistons.
I’m using oil, using around 30ml over 50 miles. Blue smoke on start up.
History recap.
Head skimmed last year, it was warped. ground in valves. new springs
Finally got her set up, and running well.
Replaced seals on ; clutch push rod
gear change sender unit
cam chain tensioner.
No more leaks.
I did think about a leak down test but I will be taking the head off so is there any point?
When the head was skimmed, the barrels looked great, A1. ( mistake no. 1 ) I didnt change the rings.
I did change the valve stem seals.
How do I proceed?
I will put new valve stem seals on again. Belt and braces. ( this time).
Q.1. Is it worth changing the rings only?
Q.2. Should I, change the pistons, and rings, and re-hone the barrels?
Finally ( for the moment ?), Can anyone recommend manufactures of pistons and rings please?
I will look for Suzuki but that may not be possible if I need to bore out.
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Yep, neverending, until everything is checked and done. Then, you have a better than new one that’ll last another 40 years.
I assume you have the correct valve tappet clearance with new head skim.
Did you check the valves in the guides? Any movement then renew, it could be oil down the guides even with new valves and stem seals. I’ve just had that exact problem.
If you are taking the barrels off then have a peek at the condition not only of the bores (measure top and bottom - if you can - and feel for a lip at the very top of the bore - check against spec) but also of the pistons.
If all looks ok then hone and new rings. If it looks suspect then bore and new pistons.
I don’t know enough about these engines to know if there’s a return on the crankcase pressure relief but I’d go for valve guides.
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