Todays Problem - Help Please !!

[GeoffMM]

Okay, i got the HT leads sorted and now all 4 cylinders are receiving a spark.

I tried to start the bike and it started but ran weak for a few minutes. After this time i touched the exhaust pipes and the 2 on the nearside cylinders were getting hot but the 2 offside exhaust pipes were almost cold.

This leaves me to believe the bike is only running on 2 cylinders !!

As i have checked the ignition circuitry does any one have any idea's? Seems strange that its the 2 offside cylinders that i believe are not firing together. When you try and rev it gently it bogs down and stalls.

Thanks in advance

[Cammo]

Take one of the plugs out on the non-firing cylinder and see if it's wet... chances are its flooded.

Bogging and stalling is pretty normal if you try to rev it when cold.

[Mananon]

Where have you got to with this so far Geoff?
Oil and oil/air filters changed etc? I saw one bike that had stood for a few years and the air filter was thick with some kind of white mold. After being stood for so long the fuel that was sat in the lines and carbs will have turned to crap so the carbs might need a clean. Check plug gaps too if you whip them out.
Let us know how you get on.

[GeoffMM]

Thanks for your help.

So far i have,

- Replaced the ht coils and leads
- Changed oil and filter
- Changed air filter
- Checked plugs and adjusted gaps

** From the guidance above i guess my next step will be to check for flooding on the offside 2 cylinders. Is there an easy way to drain this or do i need to strip the carbs down?

[Mananon]

It'd be worth getting some carb cleaner and doing the carbs sooner or later Geoff.
Was the plug wet? If it does flood, just take the plugs out on the flooded cylinders and let it evaporate off for a while.
Try swapping the plugs from the cylinders that fire to the ones that don't. That'll tell you if it's those plugs.
Down to basics, you need a spark (at the right time but leave timing alone for now), compression and a good fuel/air mix to get combustion.
Lets assume all cylinders are getting air (new filter) and a spark (the swap around will tell you if it's the plugs) that leaves fuel. If two cylinders are firing ok it might indicate that the other two are either flooding or starved.
This is a bit over simplified but a good starting point.
There's a jetting guide at the top of the workshop page that will help with getting the carbs off and apart. Check the floats aren't sticking and that nothings blocked but blow blockages clean with carb cleaner rather than poke fuse wire or something in.
With luck it's the plugs. Easiest fix.
Keep us posted mate.
Duncan

[GeoffMM]

Thanks for your help, will give this a whirl and then let you know.

[GeoffMM]

Did the jetting guide and it seems to run better but!! The 2 eshaust pipes on the near side get boiling but the 2 pipes on the offside just get warm.

Is there any way that i can check these 2 cylinders are functional without taking the head off and turning the motor over a few times to see if it is all moving freely?

[skinnydog0_0]

Are the carbs seated properly, as it's only on one side you may be pushing them down and seating them one side and not the other?

[GeoffMM]

Oh yes i double checked and the carbs are definately seated in the rubbers correctly.

IS that what you meant?

[Mananon]

Hmm. Can we confirm a few things Geoff?
You've removed plugs, checked the gap and swapped them from the firing cylinders to the none firing ones.
Replaced HT leads and plug caps.
Cleaned connectors from loom to coils.
Checked connections to the CDI.
Replaced the air filter.
Cleaned the carbs.
None firing exhausts will get warm from heat transfer. They should all be very hot very quickly if firing properly.
Have you had a spark tester on it? Should be around a fiver from Halfords. It'd be a good way of eliminating one possible problem.