650SS Running on 1 cylinder.

H

hillbone

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I swear this bike will be the end of me.
After solving the magneto problems and retiming everything it now runs happily on just the right cylinder only. This tells me i have the timing ok. I have checked tappet clearances, compression, spark. The left carby has new jets, needle is working up and down with new gaskets and tickles up. Ive rechecked over and over . When the left plug is removed and checked for sparking whilst the engine is running, there appears to be no fuel into the cylinder. I am at a loss. I did run it down the road on the 1 cylinder hoping that maybe it would clear. Perhaps the previous owner has left a rag in the manifold. Whats everyones guess before I pull everything apart (again) and look for the mystery blockage.
Cheers hillbone.
 
Spray fuel into the left intake as it's running on the right cyl.
Report back.
 
concours said:
Spray fuel into the left intake as it's running on the right cyl.
Report back.
Click to expand...
Here the offending bike. Genuine Paul Dunstall delivered 650SS. It was featured in Classic bike a while ago. According to the article, it was a dog back then and really needed sorting out. It looks gorgeous and appears to have done little work.
 

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hillbone said:
Here the offending bike. Genuine Paul Dunstall delivered 650SS. It was featured in Classic bike a while ago. According to the article, it was a dog back then and really needed sorting out. It looks gorgeous and appears to have done little work.
Click to expand...
That's pretty. 💃🏼

I thought we were trying to get it to hit on 2.

Good luck.
 
I am confused..... is this a continuation of the thread..K2 magneto 1 sided spark?

Is the magneto sparking on both sides now? If so, enlighten us as to what was the cause of one sided spark. We all wish to broaden our knowledge base, and learn from your experience.

What carbs monobloc, or concentric.

Slick
 
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texasSlick said:
I am confused..... is this a continuation of the thread..K2 magneto 1 sided spark?

Is the magneto sparking on both sides now? If so, enlighten us as to what was the cause of one sided spark. We all wish to broaden our knowledge base, and learn from your experience.

What carbs monobloc, or concentric.

Slick
Click to expand...
Yes I agree. How do we know the mag is good for sure?

When an engine is that stone dead on one side and a magneto is involved then its usually magneto.

A carb has to be miles out to not do something backfire etc if the other side is running.

If your sure the mag is right then maybe a compression test. Also if you retime the mag to the other cylinder and the running cylinder swaps then its mag not carb.
 
Swap leads on plugs only - does the problem change sides? If yes, maggy/ignition issue, if no, probably fuel.
 
robs ss said:
Swap leads on plugs only - does the problem change sides? If yes, maggy/ignition issue, if no, probably fuel.
Click to expand...
Swapping leads will not work.

On a K2F there is no redundant spark.

If you just swap leads it will not fire on the compression stroke. That's why I said you need to time on the other cylinder for the test to be valid.

The same is not true for a Morris Mag Jo Hunt type rotating magnet mag where there is a redundant spark. In that case swapping plug leads is a valid test.

In fact thinking more about it just put an extra spark plug on the lead on the dead side. Make sure the body of the plug is firmly earthed to the engine and start the bike up. If the mag is firing both sides you will easily see the spark at the plug.
 
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texasSlick said:
I am confused..... is this a continuation of the thread..K2 magneto 1 sided spark?

Is the magneto sparking on both sides now? If so, enlighten us as to what was the cause of one sided spark. We all wish to broaden our knowledge base, and learn from your experience.

What carbs monobloc, or concentric.

Slick
Click to expand...
Hi slick. I responded at the end of the last thread. It was an earth through a dodgy washer. It was supposed to be all new and the magneto guy wasnt even sure what the composition of the washer was. So he rebuilt an old set of points. Sparking nicely now but the bike still only running on 1 cylinder.
 
Am going to start the bike again and directly spray some "aero start" down the carby whilst running. If it fires then i will know its fuel. As i said, i have spark on both plugs when running. Theres no blockage in the manifold.
 
texasSlick said:
I am confused..... is this a continuation of the thread..K2 magneto 1 sided spark?

Is the magneto sparking on both sides now? If so, enlighten us as to what was the cause of one sided spark. We all wish to broaden our knowledge base, and learn from your experience.

What carbs monobloc, or concentric.

Slick
Click to expand...
Concentric. Slick. No wear. In nice nick with all new jets and slides.
 
hillbone said:
Concentric. Slick. No wear. In nice nick with all new jets and slides.
Click to expand...
I once had a situation where I had a tee feeding twin carbs (not on a Brit bike but a Suzuki with twin VM mikunis) where the petrol pipe would only feed one carb
It somehow airlocked !
I changed it to twin feed pipes and a balance pipe and all was well
 
Last edited:
Nice bike but, discard those Commando silencers and find some correct Dunstall Decibel silencers
 
Triton Thrasher said:
Concentrics are prone to pilot jet blockage.

The timing certainly has to be checked on both cylinders.

If the magneto has manual timing control, fully advance it.
Click to expand...
Yes the pilot bush blocks easily but the dead cylinder would still chime in when the engine was revved
 
baz said:
I once had a situation where I had a tee feeding twin carbs (not on a Brit bike but a Suzuki with twin VM mikunis) where the petrol pipe would only feed one carb
It somehow airlocked !
I changed it to twin feed pipes and a balance pipe and all was well
Click to expand...
Oooh! Thanks
 
hybridracer said:
Nice bike but, discard those Commando silencers and find some correct Dunstall Decibel silencers
Click to expand...
Yeah it had horrid aftermarket silencers when it bought it that even the magazine criticized. I fitted the spare commando ones last week. Fitted perfectly.
Keeping an eye out for decibels.
 
baz said:
I once had a situation where I had a tee feeding twin carbs (not on a Brit bike but a Suzuki with twin VM mikunis) where the petrol pipe would only feed one carb
It somehow airlocked !
I changed it to twin feed pipes and a balance pipe and all was well
Click to expand...
 
Mine feeds into left carb first, then thru to right carb which is the cylinder thats firing.
 
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