A A A A Author Topic: Engine displays rough Operation until it reaches operating Temperature.  (Read 237 times)


The CX Displays Rough Operation until Operating Temperature is attained.
Checked all Avenues associated with Air Intake, Carburetting, and Fuel.
Wonder whether it could be associated with Fuel.  :crash:


I have eradicated the Problem on numerous occasions by cleaning the Jets with Carby Cleaner & Compressed Air.
But the problem soon reappears. Wondering it the Carburettors are just fouling and need Constant Cleaning & Maintenance.


It's common on these to have small cracks in the air intake manifold rubbers, which will cause rough idle & improve with heat.

But that doesn't explain why it comes good when you use a fuel cleaner & compressed air.

If you just put a fuel cleaner in the tank, you might find that you have condensation (water) in the fuel & it settles to the bottom of the tank.

I'd give it a run, with a normal car fuel injector additive in the fuel tank.  That would help to clean the whole path that the fuel travels.


Thanks for the Info doddsy - The intake manifolds have just recentlyn been replaced. I've checked for change in Engine RPM by spraying the Intake Manifolds and Carburettor System with Carby Cleaner. No apparent change in Engine RPM. But I have cleaned the Carby Jets with Carby Cleaner and Compressed Air. The Problem imediately is rectified, then after a couple of days, it reverts back Rough Idle before it reaches operating Temperature.

I'll investigate the Fuel Tank Scenario, you mentioned and see if it rectifies the Problem.


Are you using an in-line fuel filter? Any sign of rust in the tank?

Any signs of blockages in the emulsion tubes? Could be a partial occlusion of the pilot jet/other passageways that is not being fully resolved by carb cleaner and compressed air. I find that these bikes really benefit from a good ultrasonic clean, and that often compressed air and carb cleaner is insufficient for a complete clean.

Did you remove the pressed in idle jet (or screwed in for the later carbies)?


Thanks for the Info doddsy -
Yes, I have always used an inline Fuel Filter, I have just replaced it a couple of weeks ago, It's longevity was approximately 6 Months. I drained the Fuel Tank in the Process and there were Globulated Water Droplets in amongst the fuel seen in the container. I ride the bike daily, which I have done for the last 30 years. Without any Major Hassles.

So to ease the Rough Idle, I've been draining the Carb Bowls at night, so as to try and maintain a smooth operation next day when riding the Machine.
But it does on occasions make a slight difference but not really curing the Rough Idle before reaching operation Temperature.

But, I will check out the Pilot Screw Seats and clean them with Carby Cleaner and Compressed Air this weekend and add a Fuel Cleaning additive into the Fuel Tank and let it Clean the complete System, check whether the problem was rectified.

My previous Actions for Cleaning Carbys were to remove the Carby Vacumm Piston, spray cleaner into the Large and Small Jets, also around the Pilot Jet opening. Then let it soak over night and clean the Carby's with compressed Air next Morning.
The Machine starts at the First Revolution and runs smoothly, then returns back after a couple of days to rough idle before engine reaches opeerating Temperature.

The Machine seems to run fine with no hassles of Rough OPeration when reaching operation Temperature.


Problematic Process of Elimination : Thanking everyone to their input in my Fuel Diagnosis. :crash:
Engine Operation does run smoothly after Cleaning and Air Compressing the Carburettor System.
But systematically returns to the usual Rough Idle Operation before Operating Temperature is reached.

I am surmising that I have water Settling at the Bottom of the Fuel Tank.
I'll add a Car Injector Fuel Additive to see if the problem is relinquished.
If not relinquished from adding Car Injector Additive.
I'll proceed to more radical procedures to rectify the Problem. :hatoff:


Like JC has suggested above I think your carbies probably need a full tear down, clean and rebuild. Just cleaning the jets is often not satisfactory. Even using fuel injector cleaner will not properly clean calcified emulsion tubes etc.

Google search “Larry’s CX carby cleaning” and you should find websites with a brief overview of the full tear down, clean and rebuild procedure. You can also purchase Larry’s book if you want to, it is very comprehensive.

Alternately CX Phreak (Mark) on this site has done the job for others and may be able to overhaul yours too.



Seagrass : Thankyou for your Infomation on Carburettor Ultrasonic Cleaning.

I knew it would be no easy Fix with the issues of Correct Carburettor operations.
As I have dismantled the Carburettors many times before Cleaned them as well as I could.
Re-Assemble them and after a Short period, reverts back to rough Operation before Operation Temperature is reached.

Thanks for the Links, I'll get it underway and rectify the Problem.


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