MZ/MuZ Riders

Hi All,

I bought a 2001 Baghira 660 with 20000km about a year ago, which had the following modifications done by the previous owner;

• Wiseco 101mm 11:1 piston
• Hot cams stage 2 camshaft
• Mikuni TM34b65 Carburetor
• Kibblewhite valve springs
• Solid balance shaft gears (without springs)

I have rode the bike a few thousand km and have observed the following problems;

• Running very rich, I fitted a wideband 02 sensor and gauge to try and tune the carb, (also rebuilding the carb with new pilot needles which had broken tips. Also new needle valves as the old ones were seriously corroded.
• Very noisy valve train, I thought this might be due to the hot cams.
• Burning oil, crazy amounts like 500ml per 200km. I don't have any oil leaks, just a very small residue from the rocker cover. I'm guessing this would be either valve guide seals or wore rings.
• Occasional going into neutral between gears, other than between 1st and 2nd;) Maybe this is just sloppy gear changing from me.

So mainly because of the massive oil consumption I decided to take the bike off the road for the winter and start with the head removal.

With the engine still in the frame I removed the head. The first thing I noticed when removing the rocker cover was how out of line the timing was. It seems that the previous owner had adjusted the valves by using the H mark on the flywheel rather than the I. This would probably explain the noisy valve train as it puts the cam gear out by one tooth.

The piston Skirt was a little wore and the barrel was glazed with some small scratches, although everything seems in spec. But then I found something that made my heart sink, when the piston was remove I discovered that the wrist pin was loose in the small end, both seemed to have score marks. This could mean only one thing the engine had to be removed from the frame and disassembled:(








So firstly all the flywheel side components were removed, whilst stripping this side I noticed that two o-rings were missing from the oil channels. Then the clutch side was stripped and the gearbox cracked open, this was interesting when all the gears flew everywhere:) The gearbox casings separated surprisingly easy without using a special tool, is it normal for the big end bearings to slide easily on the crankshaft?

So now I am left with a million questions of what to do next, this is where I need you expertise:)

1, Piston and barrel- I'm stuck with these options.
a) Just replace the piston rings wrist pin and hone the barrel.
b) Buy a new wiseco 101mm piston kit and hone the barrel.
c)Buy a wiseco 102mm piston kit, bore and hone barrel.

2, Con rod and Crankshaft.
a) Remove the Conrod, maybe by myself (does anybody know how difficult it would be?) and replace with new OEM or aftermarket.
b) Remove the Conrod and machine the small end hole bigger and add a bronze bushing (has anybody done this?)
c) Replace the whole crankshaft with used OEM or new aftermarket, do any companies like wiseco do compatible crankshaft for this bike?
3, Extra modifications whilst in there.

a) I was thinking of upgrading the crank and or Con rod, any aftermarket recommendations would be welcome.
b) I've read about some of you guys lightening the flywheel and balance shaft, this would be easy to do with the CNC machine so just wondering if anybody could advise me on how much material to remove without sacrificing reliability or shaking the bike to death. I'm not racing the bike or anything although it would be nice to pop wheelies:)
c) What else should be replaced when rebuilding the engine? All the bearings seem OK in the bottom end but is it best to just replace them all anyway? What gasket kits are commonly used as the OEM ones seems really expensive, I was thinking of using Wiseco. should the cam chain be replaced? if so what aftermarket ones are recommended.

Any advice would be appreciated.
Cheers Matt.

You definitely need to bore that cylinder. What's the big horizontal gouges? It looks like the engine was seized at some point and the rings were rusted to the walls.

As for the crank and con rod, may as well take it to a professional to have it checked against the specs and rebuilt with a new rod. I think Carrillo makes rods for the Raptor that will fit on the MZ crank but the crank ends are different, probably an XT600 crankshaft. I'd stick with the stock crank if it's salvageable.

The lightened balancer shaft and flywheel would be nice but you certainly don't need to do that much modification to get the bike to do power wheelies. Mine pumps out over 60hp at the wheel with intact balancer and flywheel. There's a link to the flywheel mod drawings in my build thread if you want to go that far. The lightened balancer will reduce rotating mass for sure but also changes the rpm at which the bike shakes the most. If memory serves me correctly, a completely symmetrical balancer will make the bike shake most around 4000, but will be smoother above and below that rpm.

Cometic gaskets and Wiseco timing chain for the Raptor did the trick for me.

The decomp system can be a bit fragile if you are running it at high rpm all the time. With the cam profile I chose, there's no need for one anyway, so I just removed it and modified the cam shaft to maintain oil pressure through it. You can also find some products for the Raptor to beef it up if you want to keep it intact.

I'm no pro but these are the things that I thought might help you and they are to the best of my memory. Always get a second opinion.

Cheers edfmaniac for that info.

I will definitely go with your advice and re bore that cylinder to 102mm, it hasn't seized or anything since I 've had the bike but anything may have happened with previous owners.



Probably won't bother with lightening the balance shaft or flywheel then, maybe the bike just felt so weak because the timing chain was so far out and the bad cylinder condition.

Those Carillio Con rods look so sexy, although the price is rather steep. I am still playing with the idea of machining the con rod small end 1mm larger and pressing in a bronze bushing, whilst it's still connected to the crank. Although this would weaken the con rod somewhat so I would like to find out if anyone else has tried and tested this.

Matt.

Changing the rod is a job for a shop, unless you have experience and a big press. A new rod set is available and only a couple hundred bucks; change the main bearing too. Also, I'd have someone go over the head and make sure everything is OK; not a normal problem point for these bikes but I'd suspect everything at this point. If go 101 on the piston, but I'm conservative.

I have a rod set in near new condition I'd sell for 50 bucks.

If you have the time to order one from Europe, changing the 1st gear out for one from an Szr660 is a great improvement; makes the gearbox much closer ratio and more appropriate for a street bike than the stock one. The part numbers are here on the MZ forum somewhere.

RE the timing chain - if the etensioners look worn I'd replace both. If they look OK then I wouldn't change either. But that's just my opinion.

Hi sam, thanks for the advice,

Could you please send me some more info and photos of the con rod kit that you mentioned for sale.
We have a press at my work and I can fabricate tools so maybe I give it a try. If I get too stuck I can always go running to the Harley shop we have next to us:)

They make it look fairly easy in this link, although I'm sure it would be harder.

http://www.instructables.com/id/Rebuild ... rankshaft/

You're probably right RE putting your one rod set in. I've always had acess to a real good crank person so I let him do it. I'll dig out my spare rod, and try to get a good pic or tow of it tomorrow. It came out of a bike with less than 5k miles,that had a top end failure.I bought a new rod as an insurance policy before,rebuilding. When I had the crank apart i found that the old rod was fine, but I wasn't about to return the new one I had...

OK, they're good, but not "near new" as I originally remembered. You can see wear on the pin but cant feel it, and there is a hint of siezure on 1-2mm of the emall end. I'm sure this would rub out and not even need a hone, but its there for you to see. pics are the best I could do with my phone...

25 bucks, shipped. I'm not out to make money, just to make sure I dont lose money keeping stuff like this around.

Sam

Hi Sam, cheers for the pictures, they look fine and that is a very generous offer.

Although I have decided to try to bush the small end, as the rest of the crank is in spec.
I'll post the details but the plan is to clamp the rod and crank to the CNC maching, machine from 22mm -24mm, press a bimetal bushing, drill the oil holes.

This is experimental for me so I might end up needing that rod later;) Hopefully I don't blow the head apart.

Matt.

Here's a chart that may help you decide how much material to remove and they probably have a bushing you can use too. http://www.crower.com/rod_bushings