KLX 250 roller bearing head

[cloggy]

I've just discovered my spare engine has a roller bearing head. Were these standard towards the end of the production run and is the power any different?

[grouty]

Does it just have a roller bearing on the cam chain side, and a plain (in the alloy) one on t'other ?
If it does, then that will be the later C model if it is a KLX motor. Good old Kawasaki finally woke up the the shortcomings of the original set up.
As far as I am aware the cams are the same. Not sure if the head is from a KL or KLT.

If it has bearings both ends of the cam, it is possibly a Megacycle conversion.

Have you got your KLX up and running yet ?

[cloggy]

 Thanks Grouty
 It's a Kawasaki head, no klx markings on the cam sprocket, which is indented to line up with the cam and fastened with a central bolt.
 I've raced the KLX three times, a welsh forest rally where the rear brake shoes disintegrated, the Hot Trod in Northumberland, where I discovered that the brake shoes had disintegrated, and the footrest half fell off; and the Doman Hill twinshock enduro where the sump guard came loose. I think I may have had a set of fork legs off you via ebay.
 I found that although it would run happily, the jetting was way off. I have the needle on the top notch and am running a P-O needle jet. I  later dropped the main 5 to 135 and now it takes 5 minutes to warm up so I probably should raise the needle one notch. I took the head off to fit new valve seals but it is still burning a lot of oil till it gets down to the last litre. Also the gear change misses a fair bit when racing so I took the spare out of it's frame this morning and that's when I realised.  The head in the oil burner has an aftermarket cam and a phospor bronze bush and revs like crazy with it's bigger bore exhaust. I took the head off the spare to check the barrel with the intention of swapping the heads.
The spare motor seems to have a smoother gearchange [at rest] so we'll see......
 I can see why these things never finished a Dakar.  You have to be really on top of checking the fastenings, you don't have a spare sump guard clamp do you?

[grouty]

Sounds like you're having more fun with yours than I am with mine at the mo. I took the engine out of the frame for the first time in 30 years at Christmas ! Oval bore because the big end had gone west ! So, frame, swingarm painted and motor being rebuilt. New 262 piston and fresh barrel.
Rear brake shoes seem to be a pain, mine wear out in a few months. Never had them break up though. Replace the springs on the shoes though. They have a habit of breaking and chewing things up. If you have a worn drum, there are oversize Yamaha shoes that fit.
I had an issue with gearchanges earlier last year. Turned out to be my change of boots from old soft classic ones to modern "no bend" things. I was convinced that there was a problem until I went back to the old classic boots. I had to re-teach myself how to change gear.
Exhausts with 1"1/2 dia are the best. As far as I am aware there were 3 primary pipes made by Technical Tubes in 1982 for the army ISDT team. One spare, and two fitted to bikes. The two bikes in question had 262cc kits fitted. BSA type rear silencers were fitted at the time but had to have inserts stuck up their rear end to pass the noise test. The may well have been other primary pipes made since then though. I am just about to have one made for mine.
Cloggy, see PM for info on spares. It was not me that sold the fork legs, but at a guess it was Paul.

[cloggy]

 Thanks for the PM. I found the second engine to be sound. We did half a days trail riding an the KLX and the DR. One small oil leak was the only problem. I had the exhaust patched. It's a bigger diameter than standard. I got back, sorted the leak and left it running to check. It stopped. It reluctantly started only to stop again. No spark. I have spares of the electrical components but no spare time till the back end of june. Swapping plugs and coils did not elicite a spark. I'll check the old coil on one of the DRs. Does the exciter coil  ever stop exciting?
On a brighter note there was another KLX at the last event. With a 262 conversion ,bigger pipe and mini SuperTrapp, and a non standard carb. The rider said I was pulling away in a few places but that's probably due to gearing and my weighing less.
 I copied one the threads here and gave it to him  the next day at Red Marley

[TM BILL]

I think you will find the KLF 250 farm 4 wheeler head fits a KLX and the cam runs in bearings  Google KLF 250

[grouty]

I have never had ignition woes with the old KLX (touches wood !).
Have you checked the engine / frame / ignition earths ?

I have been running 262cc for a year or two now. Goes much better. Just need to do the 1"1/2 exhaust and 34mm Mikuni carb bits to go with the new Megacycle head.
The only part I cannot find at the moment is "time" 

[Trent Farlow]

Good to see the humble KLX has some dedicated followers - Can some one advise me what piston you use to punch the KLX out to 262 cc - and does it make much of a difference?  Is 262 cc as far as you can go with the cylinder in stock form?  Also does the Megacycle cam make a difference?  Thanks guys.

[grouty]

I just ran mine as standard setup, but with the 262 piston. I use an MTC piston from Joe Hooper in the USA. It does make a small difference though. Seems to pull better right through the range. The piston will need 1mm filing off the skirt to clear the crank webs. As standard the valves clear the piston crown happily. Not sure with the extra lift on the Megacycle though.
I have not put the Megacycle converted head on yet. The main difference with this is that it supports the cam on two needle roller bearings. You will need to convert your standard head to accept the inner bearing. Easy to do with a Dremel.
Full instructions come with the camshaft. The cam chain cap on the left side needs to be bored out to accept the outer needle roller. This is a bit more tricky as you have to make sure it runs concentric with the cam for obvious reasons.
I ended up making a large steel jig to clock off the machined area for the big o-ring as the mating part in the head would have been machined together with the cam housings. The joy of a large mill at work !
Usually Megacycle will do an exchange on this cap. Just that they didn't have any blanks a while ago. I now have three of them done and ready to go.
The liner is a bit thin with the 72mm bore, but seems quite happy. I think any more and it would require a new liner and some machining.
The man to talk to here is Derail. He is the guru on getting more power out of these things.
Trent, if you need details on the piston supplier just send me a PM.

[Trent Farlow]

Thanks for that Grouty - I think Wiseco do pistons that may fit so will research those - will also contact Megacycle and order a cam from them.  The old KLX's are great bikes. handle well, cheap for parts and look great too. Just got to find some more power but I know its in there.

[grouty]

This is the MTC piston. Silicone free drag racing jobbie. Used in pre-78 KZ1000 motors.


Note that it does not use circlips to hold the pin in. High quality teflon buttons are supplied instead. Makes removing and re-fitting the piston a doddle.
I have never been a fan of Wiseco pistons myself. Some swear by them though. If you do a search on here you should find a thread by Derail that gives you the Wiseco part number, along with a load of useful info.

[cloggy]

 One of the kawasaki pistons for a KZ1100 is supposed to fit. I did research it a while back and they came in three compression ratios. Looking at your piston Grouty that looks nothing like the flat topped standard so is that  a pretty high compression? If so does it run on standard pump petrol? From what I've gleaned the KLX was possibly overvalved and definately over carbed so what seems to happen is the engine produces far higher % increase in  torque as against horsepower; ie it's more efficient per  firing cycle  across the mid range once it's been bored out. Still haven't had time to fix the spark. I'll check the exciter coil first. I have a Multimeter.

[grouty]

From the info that Derail gave me, the piston eqates to the one I mentioned above. I think the later models of KZ1000 used a bigger piston pin. The KLX is (I think) a 17mm dia affair. I did look at the 1100 pistons but was not convinced they would fit. My piston is quoted as a 1050cc conversion for the KZ1000 that runs at 10.5:1 in the KZ. It may run at more in the KLX. Just make sure the piston is for the early KZ and not the later ones.
If I fill up at home I use my race mix I keep for the 73 CCM. That is 97 octane super unleaded with 20% mix of 114 octane leaded race fuel. If I am out green laning I have to top up with super unleaded. Use the normal 95 octane and it will "pink" it's way home !
Derail has mentioned that increasing the valve size would make them hit each other on the overlap. I am going to try the Megacycle head with standard valves and carb.
The cam I got from Megacycle is the one intended for mid/high rpm power. Maybe I should have chosen a different one, but I won't be able to tell until I have tried it. There is a choice of three on their web site.
I reckon you are right about the power/carb thing too. Mine was a much happier motor with the 72mm bore.

[cloggy]

I've no idea what cam I have but it has a bit more duration than the standard cam. The lift doesn't seem radically altered so I don't think it is extreme. I have no idea what the springs are either but am not too worried as it will do around 70 on a 44 and nothing has touched either then or on multiple missed shifts. Thanks for explaining the piston pin size change. At the moment I am getting more speed out of the bike by losing weight. It's the most cost effective option, and the only one I can presently justify in these straightened times.

[cloggy]

 Changed all the ignition gubbins one by one, turned out to be the generator coils.