MZ/MuZ Riders

Thanks for reminding me that I could have checked the valve tolerances. I had no idea. There is always something that could have been kept in better running condition and I am embarrassed that it was something that was easily resolved. Are there any reverse threads that I should be looking out for? Thanks.

I think you can be forgiven as it hasn't popped! I'm certain from memory they're all normal thread, the only one I was unsure about was the flywheel nut, it was so tight I was unsure if I was going the wrong way with it. I busted it off with my windy gun and it was normal thread too.

it is common practice to mark a reverse thread nut with a mark ..
see the attached picture at the end of the red arrows

torch tanks have nuts like this also so they do not get hooked up wrong
the rt125 crank nut is marked like this
dave
as always click on pic for bigger view

Thanks David! Unless anyone knows of a shop that they know has experience with porting our head successfully, I'm going to send mine off to a guy that was recommended on one of the Raptor forums. He charges $350 for Stage 1 port/polish and head inspection/cleaning/rebuild, plus any parts that need replacing.

edfmaniac wrote:Thanks David! Unless anyone knows of a shop that they know has experience with porting our head successfully, I'm going to send mine off to a guy that was recommended on one of the Raptor forums. He charges $350 for Stage 1 port/polish and head inspection/cleaning/rebuild, plus any parts that need replacing.

why not investigate whats involved and have a go at doing it yourself , i guess the main part of the proscess is the polishing of ports , Any good multi tool and a bit of patience would easily achieve this,,enlarging the inlet is another trick,remember these are not two strokes , theres not alot you can do apart from polishing , enlarging the inlet port and re seating the valves,,well thats all you'll get for $400 anyways.

I'm not going to spend the amount of money that's going into this bike and guess about the porting. If it's all hype, I'll probably never know and will at least feel good about having it done by someone who's been in the port sculpting business for over 20 years.

The casting on the 102mm cylinder that I bought off of Ebay really looked bad next to the OEM 100mm cylinder so I'm having the OEM bored to match my 102mm piston.

Kibblewhite spring kit is in the mail and I contacted Megacycle about doing my cam. Very pricey for the new cam profile!

DAVID THOMPSON wrote:it is common practice to mark a reverse thread nut with a mark ..
see the attached picture at the end of the red arrows

torch tanks have nuts like this also so they do not get hooked up wrong
the rt125 crank nut is marked like this
dave
as always click on pic for bigger view

Turns out that the clutch basket nut has those markings on it. I noticed them on the fiche when looking up lock washer numbers and double checked my engine.

Edit: Even though the clutch nut had those marks, it was conventional thread. Go figure!

How does one lock up the engine or hold a back up on gears and flywheels while trying to brake the nuts loose, or especially when torquing them during reassembly? I realize that an impact wrench will help take things apart but putting them back together is a more delicate job.

Thanks

Had some time on my hands and decided to match the carb spacer and head ports. The amount of flow gained by matching these, as well as the union between the intake boots and the spacer should make for at least 1/2hp to 1hp. There was a pretty good bottle neck effect in the boots and the large port on the head got a full 1/8 of an inch removed from the far right hand side. Hopefully the machinist will appreciate the head start and do a really good job for me.

Initial quote on powder coating the frame and swing arm look to be anywhere between $450 and $600, depending on how they classify the frame: small, medium or large. Sounds a little high to me but I don't know jack about it other than seeing it done on video.

Update: Revised quote was $300. That sounds reasonable.

Just got the OEM cylinder back from the machine shop. Instead of wondering if the aftermarket cylinder will work right, I had a moment of clarity and called the local engine shop to see what they'd charge to bore my OEM. Turned out to be a real deal. The person quoting me the job didn't realize that I was taking off so much material and then refused to let me pay for the extra work they did. Sometimes life gives you lemonade.

The head should be done early next week. Then all that needs to be done before engine assembly is to pull the $&^%*# flywheel off to machine it down, choose a cam, and replace the timing chain. Oh, and I need to address the auto decomp mechanism too. I think I just need to buy some aftermarket pins to replace the press in stock pins.

I've never read anything about the oil pump in these bikes but some of the Raptor guys replace theirs every time they open up the engine. Should I worry about that on the MZ bottom end?

Doing a similar job to mine! only on far less of a budget, going to try to do as much as i can myself.
Agree about the tank too lol, i have one off a tzr250 3ma to go on i was gifted. ..or maybe i'l get a cagiva mito and shoehorn the engine in if i really want the project to take years!!
Did you weight the stock subframe off yours lol? it weighs twice that of a little vfr400! same job with the footpegs. Little things all the way should transform the performance of your bike allright
Tried my mz with my tzr250's rear wheel while i was waiting on a tyre to come in a few years back and the bike felt like it turned a bit quicker and all.

The swingarm is also pretty heavy but there are limited options with that. My sproket carrier spun on its bearings and took a big lump out of my swingarm So from being up in a breakers i understand an 88fzr 600 one with the skinny back wheel is an option, but i cant give any details as to fitting or any of that yet, engine is the first job as its already in bits! due to big oil consumption..

How much blue-ing did your crank have btw? i know a bit is to be expected from factory but i wonder if i have a touch more than most..

Any pics of the end job of the porting too? much different from stock can you see?

Love threads like this, good inspiration for my own build

I noticed the colors on the crank right away but don't have much experience in engine building outside of rc car racing. I figured that it was all manufacturing process because for the crank to get hot enough to blue steel, it would instantly vaporize oil. Those were my thoughts anyway. The head is still in the shop because they asked me if they could take a little extra time due to a busy counter at the shop last week. I'm in no hurry as long as they do a good job, and thankfully they didn't call me today. I hate knowing anything I paid for was built on a Monday or a Friday.


Here's a pic of the solid gear installed and a reminder to remove the two vented washers and the thick solid washer when doing this mod. Also a pic of some assembly lube I bought. There's no telling what's in there but it makes gears and bearings go together as if facilitated by God himself. I had a bear of a time getting the gear that drives the clutch basket to go back on the crankshaft with WD-40 alone during a test fit. One or two drops of Lucas' gooey, sticky, runny, silky assembly lube and it jumped on the shaft without hesitation. I can only imagine how happy the cam lobes will be until the oil pressure builds for the first time in the fresh engine.

Ah thanks mate! just wanted to be sure before pouring time and money into the engine
the only one i have to compare mine to is a spare motor i got for free.
Why did i get a free engine from a breakers you ask? wellll...



Good tips with that mod!