sluggish 550

[mickwinf]

hi guys,today i had a play with the k3, took the carbs off to clean out again and fit the new carb to airbox rubbers which arrived from America last week.Once they were refitted i set them with vaccum gauges,timing and valve settings etc and also fitted another twistgrip as the old one was sticking.Now for a quick roadtest before dinner.It started up first kick and sounded great, but when out on the road it seems a bit flat about 5000 rpm it dosn`t seem to want to go above that.Any ideas from you experts out there?? thanks,Mick

[totty]

You might want to take a look at this thread with similar symptoms http://www.sohc.co.uk/index.php?topic=2647.0

[z1100r]

 Obviously somethings very wrong...5,000 revs, blimey my mates got a 13,000 mile from new K3 that he dug out with the intention of a similar rebuild to my 500 - I think he reckons I'm going to be keen to help. We had a quick spin round the block on it. I hit 9.500 revs easy and it pulled from nothing in 5th all the way. I was very surprised how good it was. Its a very tidy bike anyway, but the stock exhausts are a bit pitted and with alot of use I can see them falling apart...a shame.  Lovely bike to ride though.

 Not sure what your problem is...What happens at 5,000 exactly.....what do the plugs look like. Is the advance and retard mechanism OK, are you absolutely sure you got the valve timing right. Is the throttle fully opening, is the choke closing. Are point and condensors OK, does it rev high and freely on the stand. It really is imposible to pinpoint something definate...if I heard and rode it I'd know pretty much instantly....its one of those sort of problems that require you go over everything again...have you got  a strobe..?? have you got good fuel supply...??

[mickwinf]

thanks for ideas, i have checked valve timing and clearances,static timing spot on,will check with strobe for advance/retard.Carbs have been cleaned thorougly several times with carb cleaner and compressed air, but i have not checked float hight.I do have a in line filter, will try without to see if that makes a difference, i do have a motad fitted.At low speed it seems to be ok but dosn't want to rev above about 5000 rpm, the exhaust sounds flat, as if it was on 3 cyls, but no misfire, seems to rev ok on the stand.Compressions were ok when checked before( see my other threads)I remember my old 500/4 reving right through the red line and out the other side once when i tried to outrun a gold wing!!

[totty]

Does it also come to life above 6,000 if you down change to get it there?
Does the effect get less severe if you give it a longer run out?

I richened the needles 1 notch which made a significant improvement but haven't gotten around to adjusting the jetting further. In my case the flat spot is present regardless of throttle position.

[mickwinf]

had another go at it today,rechecked valves and timing with strobe, it seems to be advancing ok.plugs were checked and found to be the wrong grade so swapped them with spares and checked fuel filter was not blocked.When stood it revs straight uo to 8000 revs no problem but when on the road it is a bit sluggish and is reluctant to rev, if i drop a gear or two it will maybe struggle up to 6000 rpm but is not happy.it does seem to be a fuel type problem but the carbs are clean and the tank vent hole clear.Thanks for all the advice, i feel a bit isolated here in Scunthorpe, z1100r i wish you could hear it and help me cos i am a bit fed up!! Totty i read the thread and you have my sympathy!

[SteveD CB500K0]

Can you try it without the fuel filter in the system?

The engine uses a lot more fuel under load - reving in neutral will not necessarily show up the problem (which sounds like fuel starvation to me)

I had a 750 with that problem. Cleaning the (two) fuel filters didn't help so I removed them completely which fixed the problem.

[mickwinf]

yes Steve will try that next, didn't have any spare pipe today!

[totty]

How old is the fuel?

[mickwinf]

totty fuel is all new tank has been sealed

[Bryanj]

Air cleaner blocked or eahaust bunged, or if you are old enough to carry waterproof leggings DO NOT put them under the seat!!!

[mickwinf]

Bryan air filter is new no obstructions did wonder about motad exhaust will try another system see if that improves it

[z1100r]

 Exhaust would have to be pracitically blocked up for it to knock that much power off. You are talking about only being able to rev this bike to 6 grand on the road....theres something serious somewhere and I wouldn't ride it about too much until you find it. This serious a fault and power sap can end up in mechanical failure like a holed piston or seize.

 What sort of speed are you doing at 5,000 revs.

[SteveD CB500K0]

Should be about 60 mph

[z1100r]

 Some more Ideas...Are the carb slides the right way round (can you get them wrong i cant remember), You definately only bent 1 valve didnt you..??, It sounds bad enough to have a brake stuck on.