Cota 247 Running Lean and Overheating

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I fitted the condensor under the tank - it was still running poorly even though plug was probably 4 hours use so new plug and it improved. I took the bike down to ride with Greg Harding (thanks again) - with new plug bike started and ran fine until warm - we went for run with Greg and Ross Brown taking turns on the bike and the consensus is that the magneto crank seals need replacing .

Can anyone point me to a supplier?

[David Lahey]

I took the bike down to ride with Greg Harding (thanks again) - with new plug bike started and ran fine until warm - we went for run with Greg and Ross Brown taking turns on the bike and the consensus is that the magneto crank seals need replacing .

Can anyone point me to a supplier?

How about the suppliers that were recommended to you for Montesa parts in previous postings about this bike? They can probably all supply Cota 247 crankshaft seals.
If they are the same type as 348 crank seals, they are the same as one side of the Bultaco motor of the same era, so a Bultaco parts supplier may have them too. I bought a pair for a 348 from Don Newell in Brisbane.
The seal behind the ignition is easy to get out if you need to look at it to get the size, or have a look at a 247 parts diagram or manual. Whatever you do, use proper crankshaft seals and not the type of shaft seals that are commonly available at bearing shops. Another thing is make sure you use a gasket the same thickness as what came out for the seal holder. That gasket thickness is important for holding the crankshaft in the right position. If there are any shims behind the seal holder, they also are important for the same reason.

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I ordered the seal from Don Newell, thanks David - $33 . Hopefully I'll have it in a few days. Should I do anything with the bearing before I reinstall the seal? I checked for movement and it feels good.

The crankcase always had a small chip about $1 size out of the front that I had repaired to improve the water proofing and I now reckon that the chip was caused by someone trying to pry the seal cover off with a screw driver. I used a puller and it came off easily. There is one copper shim - does this need to be replaced? How does one tell? Everything is liberally coated in gasket gue is that a good idea?

My parts manual says the bearings are 6205/C-3 provides a number 0.99.2540SD for the seal but I guess that is an internal Montesa part number - the seal that I removed is a KOK TC12468 other numbers - 25 -40 -7 -2 -511 - as these are Taiwanese I guess it has been replaced at some stage.

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BTW - Brownie using the rmmontesa web site method of drilled our spark plus and a protractor then quartering - I can confirm that my trusty old depth measure (albeit in 64ths inch) was spot on. The 2.5 mm btdc matches the 21 degree mark exactly . So this further confirms the diagnosis of leaky seal.

On another side point when Graham brought his Cota to Greg's place I am sure he said he had used Automatic Transmission Fluid in the forks... is this ok to use? Would be good as I have loads of it in stock. Is it light or heavy? Greg reckons my forks are too stiff so I don't want make them worse.

My manual says SAE 20 or 30 from what I can tell ATF is more like a 10 weight .

[cedric van heerden]

Hi Andrew,
I use Automatic Transmission Fluid in all my forks, and have not encountered a problem yet, but maybe my riding does not require anything finer.
Regards
Cedric

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Cedric - that's great news. So far my riding would be better suited to a helium balloon it can only improve and once I fix all the mechanical problems I will have to face up to the reality of my riding limitations.

I have the heart of a mouse and the skill of a 3 legged frog - but the determination of a wily old Scot. Lets hope my skill improves before my determination kills me.

Cheers Andrew

[cedric van heerden]

Hi Andrew,
Further to that I use Auto Trans Oil in the clutch and gearbox on all my Montesa's, the only bike I have that has to run on specialist oil is my TY 175, and that has Elf HTX 740, just to prevent the plates locking up between rides.
Regards
Cedric

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Forks done and they are certainly much softer and with my new rear shock well run in - I can't wait to get the engine running again to try it all out

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Unfortunately Don Newell's wife has been been unwell so understandably I might have to wait - I wish you both all the best Don.

Cheers

Andrew

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Fitted new seal and fired her up - certainly has plenty of go and no sign of top end flatness so hopefully will have the problem solved. I will try and find time to take it for decent run tomorrow (weather permitting)