Author Topic: 3 cylinder 550  (Read 7771 times)

Offline mickwinf

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3 cylinder 550
« on: March 07, 2011, 09:33:50 PM »
hi guys would like some tips to get my k3 running better. After 28 years in bits the engine now runs, but only on three cyls, no 4 is not firing. I have swapped plugs and checked timing, also opened gap on valves  which seemed to improve matters slightly.New plugs points and coils fitted but only occasional spit back through no 4 carb, if plug lead taken off with engine running it makes no difference.When checked against earth plug has strong spark.Is it likely that it is a valve problem, the head and barrels were rebuilt by po, and i already discovered cam timing was well out!!  Any ideas welcome, thanks,Mick
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline SteveD CB500K0

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Re: 3 cylinder 550
« Reply #1 on: March 07, 2011, 09:39:17 PM »
If you have a spark on #4 it sounds like fuel starvation.

Is the plug wet when you remove it?
2022 Tiger Sport 660
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Offline mickwinf

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Re: 3 cylinder 550
« Reply #2 on: March 07, 2011, 09:43:50 PM »
steve it dosn't seem that wet when i remove the plug, so i tried squirting carb cleaner in the carb and a bit in the cylinder, expecting it to fire but no luck!
Love the 500 and 550 have a 500 called Lazarus under restoration

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Re: 3 cylinder 550
« Reply #3 on: March 07, 2011, 09:44:23 PM »
+1 on fuel starvation... float stuck shut? Pop the bowl off if you can and see if there is any fuel feed to that carb?

Offline z1100r

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Re: 3 cylinder 550
« Reply #4 on: March 07, 2011, 09:45:13 PM »
what do you mean by cam timing well out. It might have bent a valve if its that far out. Check compression on that cylinder...compare to number 1.

If you haven't got a compression tester take the plugs out and put your thumb over the hole. crank it on the starter motor. Compare the difference between 1 and 4. Should blow your thumb off if OK,  wont do much if you have a bent valve.
« Last Edit: March 07, 2011, 09:51:28 PM by z1100r »

Offline mickwinf

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Re: 3 cylinder 550
« Reply #5 on: March 07, 2011, 09:54:17 PM »
thanks for quick response guys will try again. Ref cam timing i reckon it was 90 degrees out, some "expert" did it before, luckily i only turned it over slowly on the kickstarter and stopped as soon as it went solid! hope i have not got a bent valve, i have just ordered a 12mm converter for the compression gauge which should throw some light on it!
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline K2-K6

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Re: 3 cylinder 550
« Reply #6 on: March 07, 2011, 09:56:20 PM »
I'd go with a compression check as well just to help you eliminate it if nothing else.

Have always used lab bottle with long plastic spout to squirt a small amount of fuel down the suspect carb when running and see if fires then.

Offline z1100r

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Re: 3 cylinder 550
« Reply #7 on: March 07, 2011, 10:57:19 PM »
 Well I hope your OK but it doesn't take much to ding a valve. They bend at the head very easy. I was mechanicing for a mate at the IOM tt in the very early 80's he was in the F2 race on a 460 Kirby Honda. A young german lad approached us in the paddock with his cylinder head from his 400 four. His cam chain had snapped as he was kicking the bike over to start it - it bent 4 valves badly. To get him home I took the valves to some engineering place by the harbor and put them in a lathe at high speed and just tapped them with a lump of wood until they spun true. Worked very well..I lapped them in and he put the head back on with a spare camchain we had. Got him round the Island all week and back to Germany. Nice lad he was, kept comming back every night to see how my mate had got on, we had some good sessions on the beer with him.

Offline Spitfire

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Re: 3 cylinder 550
« Reply #8 on: March 08, 2011, 09:57:50 AM »
It doesn't take much at all to bend a valve, I was turning over a CB450 engine on the bench by hand and just kissed a valve, it bent, and had to be replaced.

Cheers

Den
1976 CB750F

1977 CB750F2 In bits

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Offline deltarider

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Re: 3 cylinder 550
« Reply #9 on: March 08, 2011, 02:50:45 PM »
My first check would be to have it idle in the (pitch)dark and watch for any fireworks (sparks between HTleads/plugcaps and engine).
K3's sometimes have a problem with their carburetor venttubes. Check if they're all (4) open and as a precaution you may cut a few inches where they end (close to the centerstand).

Offline mickwinf

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Re: 3 cylinder 550
« Reply #10 on: March 08, 2011, 09:35:26 PM »
thanks for advice guys i had it running again tonight, it seems to fire on all four when the throttle is blipped but on lower throttle openings still on three, so maybe carbs are the problem after all! petrol is getting to carb ok and vent pipes are clear, no extra sparks in dark.
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline matthewmosse

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Re: 3 cylinder 550
« Reply #11 on: March 08, 2011, 09:54:38 PM »
If the fuel line is blocked or kinked or has a poor flow from a filter then I've found number 4 can go out of play. On my bike it was intermittent and due to a cheapo filter that wasn't allowing enough flow, also it was quite tight to fit a filter in so the pipe was bent at a funny angle and was restricted.
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

Offline flc

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Re: 3 cylinder 550
« Reply #12 on: March 09, 2011, 02:14:15 AM »
If the fuel line is blocked or kinked or has a poor flow from a filter then I've found number 4 can go out of play. On my bike it was intermittent and due to a cheapo filter that wasn't allowing enough flow, also it was quite tight to fit a filter in so the pipe was bent at a funny angle and was restricted.

i have to agree with this, as today on my way to work the bike started to run lean (i had just filled up)... oh great i thought im back to having a miss fire.
but turning to reserve cured the problem.
I will have a look tommorow but im sure i will find a partially blocked fuel tap.
Current bikes:
76 cb 550 import
gpz 1100 chop
z9 chop
sr 125 yam

Offline mickwinf

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Re: 3 cylinder 550
« Reply #13 on: March 09, 2011, 07:10:18 PM »
bad news.today i did a compression test,less than 50psi on cyl 4, so looks like valve trouble after all, really depressed now!
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline flc

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Re: 3 cylinder 550
« Reply #14 on: March 10, 2011, 02:43:57 AM »
Dont be.. at least you found the problem more than half the battle.
they are good fun enjoyable bikes.
take your time and reap the rewards.
Current bikes:
76 cb 550 import
gpz 1100 chop
z9 chop
sr 125 yam

 

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