ETZ 251 Re-build

[Blurredman]

So..

Quick write up, for I have now re-built two ETZ 250 engines in just a month, and disasembled another that looked like it had been under the sea for a number of years for potential re-build in the future.

After re-building my '87 ETZ 250 with a replacement crank, which turned out not to be the problem, but let's not go there-


My trusty old '90 ETZ 251 was long suffering from a slipping clutch, and had now at the mileage of 42,000 had a tendency to jump out of third gear, and become a little difficult to put in any gear, for that matter.

After entrusting my newly rebuilt steed for my commuting matters, I decided to strip the 251 engine and re-build that too. The bike has sentimental value after I purchased it in 2016 for £100 with a completely seized top end. I had put a worn original size piston/barrel on, and over the next few months diagnosed a coil fault, and implementing electronic ignition as the contact breakers would not set up correctly. I then covered 13,000 miles on it since then without any real major issue other than replacing a few things here and there.

And so.. on the bench, I take the clutch cover off and find the first problem- the gear selector disc thing (i'm not really sure what they are called) was not on the selector barrel. it was off. The reason for this? The retaining spring had come off the pin! Not sure how that happened, but it was replaced on reconstruction.

After splitting the cases, I find 40k miles and 30 years of gunk, metal debree and yuckiness at the bottom of the gearbox.. Clearly it has been well abused before my ownership- indeed when I hammered out the seized piston from the barrel in 2016- It was on 2nd oversized already!

It took a long time to get the gunk out, constant washing down with carb/brake cleaner.


But, with it clean and all the bearings removed, it was finally time to re-instate the new bearings- Don't worry- I am hammering on the old bearing, with something soft in between to catch debre. There is defiantely something satisfying about punching in, or out, bearings!

[Blurredman]

And thus, the gearbox was cleaned, and put together, and implemented in the LHS crank case with the crank. I found nothing wrong with the gears, nor with the selector forks or drum to indicate the 3rd gear issue was with the 'traditionally' found poor machining, thankfully a quick fix hopefully.



Everything went smoothly upon the crankcase construction, including the all new seals etc too. And thus, it was time to install it on the bike:




With that installed as a minimum, I installed the piston and head. From there on, I could torque up the clutch, primary drive gear, chain sprocket, by using rope down the cylinder spark plug hole.


Chain on, timing adjusted to counter a different crank and movement in the stator mounting. Clutch cover on (only problem was locating the kickstart bracket- as always), and it was time to start..
It is very smokey through liberal use of oil (ATF actually) during construction.

http://www.filedropper.com/video-1553524713

http://www.filedropper.com/video-1553524614


I have calculated the approximate costs:

Bearings: £40


Seals, Gaskets,
Drain plug (had to grind my old one off),
Primary drive (clutch shaft) bearing,
New bearing Oil seperation discs: £30


Crank: Reconditioned. Purchased whilst in Hungary: £35

Clutch with good taper: £20


Total:
£125


I don't think that's too bad. It's ready to go for a long time yet! I do need to buy a new rear chain cover as mine broke dramatically whilst manipulating the top rubber gater.
Piston is oversize again, and has been used for 2k miles- No excessive wear or scores on the piston. This probably cost £55 for re-bore and cheap RAM piston. So there's nothing wrong there either.

Perhaps I can ride back to Turkey again someday:

[Puffs]

Thanks for that report!

So the engine needed to come apart primarily because of the clutch taper (on the crankshaft), and also because of gear shift problems. The first was sorted w/ another crankshaft, but were the shifting problems caused by the gear selector disc thing not being on the selector barrel, because the retaining spring had come off the pin? Anyway, the most important question: is the shifting is OK now?

You have very nice weather over there!

[Blurredman]

Ah yes,

The old crank is worthless than for weight. I have the seized crank however from the 'spare' engine which will be sent off for re-built at some time in the future. I made sure to keep all those pesky rotor keys safe!

Well, I have yet to test the bike properly out in the real world road, but I am confident that the selector drum not being kept in place by the dog leg and disc. Their purpose is to keep the gear selection in gear. If it is missing/broken, then it wouldn't prevent the gearbox from changing selection on it's own through means of natural gearbox forces..


The weather has suddenly become very nice indeed here. It is cold.. but at least sunny and more importantly (to us British) - dry. As we say, any day is a good day if it doesn't rain.