Cota 247 Running Lean and Overheating

[picktas]

Hi
Just a thought but have you considered a partially blocked exhaust?
- would allow idle and gradually get worse as you open the throttle as too much back pressure builds up, causes a rich looking spark plug too...

- could try taking the exhaust header pipe off for a a short time to prove it - not for long though as this makes the engine run lean as there is no back pressure.

Solution would be to de-coke your exhaust...now that is the start of another thread all on its own.

Picktas

[keychange]

Thanks Picktas - exhaust is clean as - after lot's of work I had it running pretty good except it appeared to be running hot and hard to start when hot.

I know that bikes with electronic ignition using CDI's can be a nightmare to diagnose, I just can't believe how this machine, one of the most basic engine setups in the last 40 years, no battery, no valves just spark and fuel - can be so bloody complex to fix..... I know why the last two owners gave up on it

[TriCub]

How long does it take before you lose power? Does it happen in all gears and at the same throttle position or does it take a long climb up a hill for it to happen?

You still need to find out if it's ingition or fuel. See my bit further down about using your timing light.

If its an instant shut down it still could be ignition. I would think it could be a faulty stator winding as they can with time become lose and wear through the varnish and short out. This can happen after the engine gets hot or even at certain pionts in the rev range with vibration. Do you have anyone nearby with a Montesa that you can borrow parts from? Where are you from? (I see your from Dorrigo which is nowhere near Brisbane)

The bad running at idle and down low when hot could be your crankshaft seals the main culprit is under the Mag in a removable housing and can be changed with ease.

With your 12v timing light get hold of a small 12v battery. The timing light will tell you staight away if it's ignition or fuel. I have some small Model plane batteries that are 12.6v when charged that only weigh 100 grams and would run the light ok.

If the power drops off only after you have been under load for a while make sure that there is enough fuel flow into the carb. Juat take the plug out of the bottom of the carb and place a measuring cup under it(you may have to take the carb out of the manifold to do it) turn on the fuel tap and measure what comes out in a minute, 75 to 100ml should be enough. If you can't get near that flow start going back and test the flow out of the filter then out of the tap.

Happy playing.

[keychange]

Power loss is immediate in all gears and at same rev range with throttle position (wide open) - I had this mainly sorted but now it's back. Fuel flow is good - there is no blockage I can drain litres from tank in 10 minutes so easily 100ml per minute. The carbie filter is new and clean as are all jets.

I suppose my cordless drill 14.4 battery would drive the timing light as most ca recharge circuits are well over 12v - I'll try it.

Does anyone know what specs for the replacement condenser?
Thanks
Andrew

[TriCub]

You can use just about any condensor that is ment for pionts ignition. I have used VW beetle units and mounted them up under the tank next to the coil. Mounting the condensor up there keeps it a lot cooler and much easyer to change as well.

Sounds to me that you do have an ignition problem.

When you measure the fuel flow it has to be through the carb as that checks the entire fuel system, but it sounds that the problem is not fuel.

[keychange]

Under the tank - a great idea, I am so sick and tired of pulling that blasted flywheel off. Not to mention the need to locknut the stupid crankcase cover screws which otherwise rattle loose in a mild breeze.

Thanks again

Andrew

[cemoto2]

Hello Andrew, I met you at Gregs place a couple of weeks ago. I have a condensor mounted under my tank which is a Champion P/No. NC203 which I purchased from Repco. In my TY I have a Bosch P/No. GD206. Both seem to work fine. If you are still having troubles I might be able to get another coil to fit down near your points for you to try. Regards Graeme.

[keychange]

Hi Graeme

Thanks for that - have you got the condensor wired in line with the low tension lead to the coil or all way back to the points?

I went into Dorrigo today and the only condensor I could get was the very last of an old stock at the back of one the workshops it's a 0.22uf which I think is quite low (compared to most old car engines ) so it should be ok - it only cost me $10 and it will either work or it won't - I can't conceive of how it will cause any damage as there are no polarity issues. If it doesn't work I will be ducking down to Coffs early next week and will take your advice on Repco.

Have you give your Cota a work out yet ?

Cheers

Andrew

[cedric van heerden]

Hi Andrew,
I have all my Montesa's condensors under the fuel tank. Firstly remove the condensor behind the flywheel, and then just wire the new condensor into the black lead that goes directly onto the HT coil, at the Ht coil. I have used one of the mounting bolts for the coil to fix my condesors to. One thing David Lahey told me and that I have followed ever since is to make sure that the earthing points in the whole system are well cleaned so as to make very positive contact.
Regards
Cedric

[cemoto2]

Hello Andrew, just wire it up the way Cedric said and you should have no trouble. Mine goes well, its a bit tempramental trying to start it sometimes but once going its ok. I had trouble with the clutch when I first assembled it but a mate had a spare motor so I swaped parts around and got it working. Regards Graeme.