JOTA 180 Poor Running

D

dougieboxer

New member
Hi Guys

Wonder if you could give me some advice. My Jota has been running poorly (intermittently) for a while now - on start up from cold the bike idles and runs fine, pulling cleanly to max revs in each gear. Afer a few miles it starts to bog down and then runs on 2 cylinders. Sometimes it will clear its throat and then run ok for a bit, then play up again. I changed the plugs and HT leads and it ran great , then it played up again. >:( I drained the carbs, it ran great, then played up again.  >:( I just want to know to know where to look next , and the likely culprit!

Thanks for your help

Doug
 
Doug, difficult to say from what you have told us so far.

Fuel starvation comes to mind straight away.
Is there crud in the tank?
Fuel taps clogging up?
Breather in the fuel cap not working?
Tried opening the fuel cap when it starts to go on 2?
Tried the choke too?
What size needle jets?
Primary jets?

It could also be a coil breaking down.
Is it always the same cylinder that conks out? Centre one?
The other 2 (assuming a 180 Jota) fire together, so less likely to be coil-related if one of those conks out repeatedly.

I assume all the connectors are making good connection.

Give us some more to go on and we can maybe help further.
 
Hi Doug,

have you checked for water in the gas? Modern unleaded gas does suck water and over time, this sums up to quite a lot of water. As gas is lighter than water, the water stays at the ground of the tank. When you drain the float bowls, you remove the water from there but next time you open the pet.-cocks again, you get water again into the float bowls. If the water is not yet on a level it directly reaches up to the little plastic tube at the top of the pet.-cock (under the mesh filter), it only gets sucked in when you lean the bike over a bit so the level changes. That might explain why the symptom was gone when you drained the floats but returned (after the first or second corner...). Rust in the connecting pipe at the carbs could cause the same issue... big flake closing up temporary the pipe.

I would put some fuel-line cleaner into the gas (you get that at your local bike store or car parts supplier), wait a bit until it has mixed with the gas and water and ride the bike again, maybe with draining the float bowls again before you ride again. Typically - if it was the water - the symptoms are gone after just a few 100 meters.

If that was not the fault, I would check for air-leaks in the intake and exhaust system. Also check your ignition is OK and timed correctly, plug cables are not lose and everything has good connections. sometimes it is also just the little power-connection on the coils coming from the ignition or a fuse that has oxidized contacts. Put my money on the water in the tank though, as it fits best with the symptoms as I understand them.

HTH
 
to me it sounds like a valve problem,

have you had any work done to the bike recently?

it could be a valve clearance is tight and then closes to zero when the engine gets hot,does your engine run nice and (too) quietly? or

it could be a valve sticking in the guide,OK clearance wise when the motor is cold, but closing/closes when it gets hotter, and so does not shut tight,you would most likely hear a "tapping" if this is the case or

it could be a broken valve spring, which only shows up under certain loads, when more of it is required.

CLEM
 
Thanks for your replies, much appreciated.
I should have said, the tank appears to be crud-free and the fuel pipes & connections are clean and secure. I'll stick some fuel cleaner in tonight and take it for a spin tomorrow.
The engine was rebuilt about a 1000 miles ago so the valve issue could be the problem, hope not!!
I've been using Super Unleaded fuel in it - would it help using an additive as well??
 
Rebuilt?
Rings only?
Rebore, new pistons and rings?
Just valves?

Is it overheating because it is still tight and needs running in?
 
Wild stab in the dark....

Check the carb to head union.

My bike would start and run fine, but as it warmed up the inlet manifold O rings started to leak air.......
 
dougieboxer said:
Hi Guys

Wonder if you could give me some advice. My Jota has been running poorly (intermittently) for a while now - on start up from cold the bike idles and runs fine, pulling cleanly to max revs in each gear. Afer a few miles it starts to bog down and then runs on 2 cylinders. Sometimes it will clear its throat and then run ok for a bit, then play up again. I changed the plugs and HT leads and it ran great , then it played up again. >:( I drained the carbs, it ran great, then played up again.  >:( I just want to know to know where to look next , and the likely culprit!

Thanks for your help

Doug
Click to expand...

This is clearly a HKZ failure syndrom! Do you still have the original ignition?
 
1200ts said:
Does the bike have resistor plug caps? If so change them. I have seen a number of cases where they will intermittently cause problems once they get hot.
Click to expand...

I have also had this problem, of course it could be one of many problems, you need your analytical head on ! but at ?8.60 plus postage for a set of 3 you should not overlook them, as the resistors within, can break down when hot. (plug caps that is)

When it's down onto 2, find out which cylinder is not functioning, wet finger on the pipes just before the collector, feel for a temp difference. Once you know which cylinder is not playing, you can narrow down your logical search.

Remember you can swap the 2 outer plug leads to swap the problem cylinder over or not. See what you find ?
 
I had the exact same problem coming back from Italy last year. Was convinced it was a coil or plug problem.

In the end turned out to be the floats in the right carb sticking almost shut, starving that cylinder of fuel. Stopping at a set of lights for example and the float chamber would fill up and the bike would run for a mile or so before going back onto two.

In the end, I stripped the carb and got the float moving freely, then all OK again! Maybe that's it?

--
Dick
 
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