Minsk 125. CCCP era 2-stroke commuter of the people.

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Well really!
You'd think he'd at least wear a tie to these social events
Makes you wonder what end of the social scale these people belong..

https://www.bikechatforums.com/download.php?id=106648
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bikers smell of wee

virus · World Chat Champion Joined: 16 Aug 2006 Karma :

I must say, Scotts habit of wearing a vibrant hawaiian shirt really helps find him in a crowd on account of not looking like every other big bloke with a jacket and waistcoat Laughing

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own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

that_impulse_guy · Scooby Slapper Joined: 07 Mar 2023 Karma :

you dont need my praise, but as a mostly silent follower of this thread since november I'm pretty impressed you went out on a run and got back ok already, all this from some bits in boxes a few months ago. Nice job.
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Gone: Yamaha DT50lc, Suzuki DR500, Suzuki A100, Kawasaki z250ltd, RD350YPVS, Suzuki DR Big, Kawasaki AR125, Kawasaki KMX200, Suzuki GS1000S, Katana 1100, GS550M, Suzuki RGV250
Now: Suzuki GSX400X, Suzuki RF900R, NS400R

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Thought I'd have a look at the electrics today. Did a static test of the coil windings which gave an equal resistance to earth on both sides and an acceptable coil resistance between the two.

Static unregulated output was sitting at about 25VAC at idle.

On my analogue meter, the regulated output was a slight waver up and down at around the 14V point as you'd expect. I tried it with the digital meter and it was absolutely all over the place, couldn't settle on a reading and was flickering up into the 100+V range then back down again. Tried it on AC and it was also giving a wildly fluctuating reading.

I think the reg/rec is junk. I managed to score a used YZFR1 reg/rec on ebay for £35 which is a shendingen mosfet type (FH16 I think) and the proper connectors on amazon for £7.50. I think this will be a good starter for 10, see what it does with that. Even if more needs doing, it's not wrong to have it.

Also scored a pair of used shocks off somethingorother for £35. They look right and the dimensions are correct. Seller had no idea what they were off either so it's down to a lottery if the spring rate is in the right ballpark. Only bikes I've seen with shocks this length are either 125s or harleys and they certainly aren't beefy enough for a harley. The springs are progressive which is probably a good thing for my weight on a tiny bike.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Difficult to see what's exactly what on forum posts
and I miss stuff anyway
but have you got each coil grounded one side and tother's going to the RR?
if so that would be 2 half waves and a bit spiky I reckon

I'd probably first have tried lifting both wires from each coil and joined them in the middle as one connection ( no connections to ground)
then used that and each of the free end wires to connect into a common
3 phase bike RR

maybe you already did that, dunno

just did a quick scrawl on the white-ish board
i'd have tried the bottom version first

https://imgur.com/FbvcSTB.jpg[/img]
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bikers smell of wee

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Since the Minsk and MZ125 are both based on the same WW2 DKW design, I did some looking. Bore, stroke and port timing are identical. So the pressure wave dynamics should also be identical. They race MZs. So I got to wondering...

... Apparently yes they do. And only £55 delivered from Germany. Header is the same diameter, bracket is about 3" out. I feel my future may involve some plug chops.
https://lh3.googleusercontent.com/pw/AP1GczM7_P3s-I9oSXIGKRBRaiEyvocUD1iOg44EmgeMRj5YKX4Aau0LOqULjX8TCE0JphX0SHILyXKuh8Ra927qKvPMLbcQxCrFhFLrjuecqsIYbAr1hr33NEY0FAhbzO8H6inLKNtbbi6bj2iwSwYND2D3=w1557-h876-s-no
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

I had one of those on my MZ. Sportauspuff!

I'm not sure it did a great deal, but I liked it.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

A100man · World Chat Champion Joined: 19 Aug 2013 Karma :

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

blurredman · World Chat Champion Joined: 18 Sep 2010 Karma :

It might not make any difference but make your ears bleed. Laughing

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CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 17k, 1979 Suzuki TS185ER - 9k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 38k, 1989 MZ ETZ251 - 50k.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

52.4 x 57.9 on the minsk.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

I found this pic the other day...

https://www.bikechatforums.com/files/dsc02021.jpg
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Well, the exhaust bolted right on with a very simple bracket. It rode fine, not much different to the original one in fairness.

Out of curiosity, I decided to take the end can apart to see what was going on in there. Turns out it's literally a metal cylinder stuffed with fibreglass packing. Doesn't even have a baffle tube in there, there's just a long spring to stop the fibregalss from completely obstructing the gas exiting.

So no stinger on the end of the expansion chamber and a surprisingly wide exhaust diameter. I decided to make a baffle tube. Used a piece of alloy tube, necked it down with a steel insert at the exit from the expansion chamber so the diameter is the same as the standard, then a 12cm stinger section then perforated the rest of the way. All bolted back together easily with the packing round the outside of the baffle tube.

Immediate transformation. Crisp, rattly exhaust note which I associate with a properly setup 2t exhaust. Way quicker off the throttle, fewer "bung-bungs" on the overrun which means it's scavenging well. Had to wind in the idle screw significantly so it might need a larger pilot but frankly, it hardly ever uses low revs unless you're stopped in traffic and the idle is very stable. Picks up well from no revs and pulls much better through the midrange, I can stay in top gear up hills I was having to downshift for previously.

It would probably stand an extra tooth on the front sprocket now, although I might do some light offroading on this bike becuse it's very capable on dirt so I'll probably just leave it as-is.

A plug chop showed a nice clean, brown electrode but I tried the next jet size up just to see. That was too much main, caused it to bog between 3/4 and full throttle unless it was absolutely flat-out so went right back to standard jetting.

Saw 50mph on it, which is a first. Money well spent, although the standard setup on that exhaust was very shonky. I'm guessing it's for noise reasons because it is a tad on the loud side now. Probably not enough to have people tutting as you ride past but if you were doing laps of the town square all afternoon, I could see people getting annoyed.

The postman says he loves the smell coming out of my garage when he delivers the mail. Smile

Did a short video.
https://youtu.be/V2Us1UyyGZk?si=WEw2JMF-HP8fFqmd
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

A100man · World Chat Champion Joined: 19 Aug 2013 Karma :

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Easy-X · Super Spammer Joined: 08 Mar 2019 Karma :

Sounds very nice Thumbs Up

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Husqvarna Vitpilen 401, ~~Yamaha XSR700,~~ ~~Honda Rebel,~~ ~~Yamaha DT175,~~ ~~Suzuki SV650 (loan)~~ ~~Fazer 600,~~ ~~Keeway Superlight 125,~~ ~~50cc turd scooter~~

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

It's got something of an air cooled MX bike sound to it. I like!

I miss my MZ but I found an old FB post about it today that reminded me the primary cover leaked oil continuously... which is probably the gearbox output shaft seal.

I'd love another MZ 300 but I'd want a mint one, and ideally a Saxon fun again. I've got my KR1S to meet my 2t fix though, so I probably won't have one.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.