'84 MXC 250

[Montynut]

Hi guy's. I've just sold my sole and bought a MXC 250 '84 model for Pre85. The bike is in race ready condition (it won the Heaven Pre85 250 and all in this year) so my problem will be doing the bike justice ( fat chance).

The clutch cover in the water pump area is in prinstine condition and I would like to keep it that way. What is the best coarse of action to stop the Magnesium rot?

Drain the cooing system between meetings? I thought that might be a problem as it exposes the case to oxygen often.

Change coolant every meetings?

Use a particular product?

Use straight coolant?

There is a product on Ballard's site that seems to be a non watre coolant which is shown to be magnesium friendly anyone used it?

This is the first one of these 'keetles' I've had since returning to bikes. The Monties are all a little more basic crinkle fins and all

[ozktm151]

Greg, for what its worth I have not done much to my 84.99999 250. When I seized it at Lakes and pulled the top end I checked the waterpump area. I had to bog it up originally and noticed that the bog was a little flakey now but I dont think there was too much more mag corrosion. I have never drained it after riding etc but I cant tell you what is going to happen in the future. I use Nulon concentrate. Maybe its ok maybe not.
See you next year. Bill

[Montynut]

Thanks Bill, after our little coming together at Canowindra in the last race after my complete stuff up of the sand section  thought you mightn't welcome me to the KTM fold

[Luke Lloyd]

Hi mate, i have an 84 Honda CR250 and these suffer from the same problem around the water pump area, and it to has a magnesium cover, i have been told by a competent mechanic, who is in his sixties and very experienced, to only use fresh water, no additives at all and change it regularly. i hope this helps

[dalesween]

I dont know if KTM's problem had been fixed by 97 but i bought a KTM360exc off a guy who used to ride enduros with Wattsie, a Maffra Motorcycles bike ,anyway the guy i bought my bike off had done about 150kms before he had a workplace accident and could'nt ride the bike again,when i went to look at the bike he said it had been sitting for 9 years(in a warm garage under cover) so he drained the coolant out and had distilled water in the system?I got the bike home and pulled the cooling system apart to look for corrosion but everything inside was like brand new,now im riding the bike every now and then and i am using a 50% coolant water mix and all seems fine,does anyone know the good info regarding this.

cheers Dale.

[Big John]

I had an 84 KTM 250gs, 3 cluch cover's in the 4 year that I owend that bike. Castrol anti freeze 50/50 mix with distilled water. Maybe I should have just used water.

[pmcburney]

I could be mistaken, but didn't KTM go aluminium on their clutch covers in the late eighties?


I had corrosion issues with my '86 500 and I managed to track down another cover that, as far as I can tell, is identical but for the fact that its aluminium rather than magnesium.
It's noticeably heavier, isn't stamped 'magnesium' and has not one jot of corrosion even though it's plainly second-hand.

Pretty sure it came off of an '88 or '89 model.

Otherwise, distilled water, drain every meeting.

[Nathan S]

When KTM was having corrosion issues with magnesium clutch covers in the early 1990s, the recommended solution was to run straight water.
Don't know if it worked or not.

I've had fairly good luck with painting the exposed metal inside the water path. I bead blast the area first*, and use a good epoxy paint. Can't say how it works over multiple years, but so far, so good. A good sealing layer of paint also helps to stop corrosion getting under the edges of any existing Devcon/JB Weld/whatever.

*Remembering that I've been doing it as part of a repair, not just prevention.

[Nathan S]

Hmmm... something about doing as I say, not as I do.

In a mad rush before Canowindra last year, I put some epoxy into an average clutch cover on my '84 KTM125. Fitted it to the bike, and filled it with distilled water.
Then I discovered the clutch slipped, so it got left in the shed until last weekend.

There's a ton of new corrosion in there - way more than I'd have thought possible - if it was an aluminium part filled with seawater, I'd still be surprised at the amount of corrosion in there...

I've gone in hard with the JB Weld and the good paint this time - there's literally no magnesium that is touched by water now. We'll see how it goes, but I think I'm just going to drain the water everytime the bike isn't being ridden.