PUCH 250 SGS

Restoring a barn-fresh 1966 Sears Allstate

Open heart: open wallet

Puch_head_off_pistonsI pulled the head and barrels to see what damage has been done – alas it is the front piston that seized and the rear piston has evidence of oil film loss and scraping. Interestingly these are on the sides that face each other.

I did some research online and it seems that there are four possible culprits:

  • lean jetting
  • low/no oil in mix
  • air leak (causing localized lean/hot spots)
  • timing

I can pretty much rule out air leak and I’m going to go out on a limb and rule out jetting as I believe it is stock.

A mechanic saw the photos and opined that it is most likely timing. This could be so as I haven’t touched the timing since I got the bike. I did reduce the oil to the minimum setting, as I was using modern oils and assumed I could get away with less smoke. Perhaps at open throttle it needs more.

So, clearly a bore or hone and new pistons are in order. The question is why did it seize. I would like to have some confidence in diagnosing the problem before slapping in a new set of pistons and twisting the throttle again.logo_koenig

Clearly this isn’t a unique experience. I found this photo on the net, clearly toasting pistons is a Puch thing. I was hoping to get away with a hone an a set of rings but, clearly, new pistons are needed. So open heart surgery has led to opening my wallet. Those pistons ain’t cheap.

It seems Elko/Konig is the only game in town for replacement pistons.

To think she was so happy just a few days ago….

posted by Fastback in mechanical,parts,Puch,Puch 250 SGS and have No Comments

Seized

old_plate

Been a while since this plate was used – shame to cover up the sticker.

I guess expecting reliability from a 49 year-old un-rebuilt engine is unrealistic. I was happy so far as I’ve only addressed cosmetic issues and suspension. My luck has run out.

I was on my way from the licensing office to work on my first “legal” drive. Was doing about 60-65km when I lost power and then the rear wheel locked up. Pulled the clutch and pulled over, the engine turned over but it feels like compression is down, although there is compression. With two cylinders and a shared space it is difficult to tell which cylinder has an issue.

Question now is, full rebuild? Source of the problem? Lean carb, oil delivery – cable or pump? The bike was running great a few days earlier and did the same stretch of road no problem.

This page might come in handy when I get the head off, it shows how to read the piston damage from a seizure.

http://www.theultralightplace.com/READING-2-STROKE-PISTONS.html

posted by Fastback in mechanical,Puch 250 SGS and have No Comments

Finishing touches

Final push to get the Puch 250SGS on the road.
Certified. Appraisal booked. Tightened the seat springs (which necessitates seat, gas and oil line removal…) Handlebars fitted with better rubber mounting and bars repositioned. Float-bowl heat-shield fabricated out of old coffee-maker stainless.
She’s ready.

posted by Fastback in Puch 250 SGS,restoration and have No Comments

CVMG Paris Rally: 2015

Another Paris Rally, great weather – here’s a few pics of what caught my eye this year.

 

 

posted by Fastback in cool bikes,events/shows,Puch 250 SGS and have No Comments

M125 – seize the day

I was in the process of ordering parts for my ’66 250 SGS when I thought I “might as well” get fork and shock seals for the M125, save on shipping.

The M125 has languished in the corner of the garage since I bought it. The engine was seized and the kick lever moves up and down – something is broken in there. I have always hoped that a squirt of oil down the spark plug hole and  and a quick fix on the starter mechanism would have em laughing as I bing-batta-binged around.

Starter chain broken.

Starter chain broken.

You know how “while I’m at it” syndrome works; I thought, no point ordering fork seals for a bike that won’t start, so I cracked open the kick starter and discovered a broken chain. Great, not too hard to replace, I hope. I will have to hunt down the owner of the bin seen here.

Next issue was the seized piston. When I first took the head off I was greeted by a gritty, twiggy, sandy sludge sitting on top of the piston. I guess the previous owner let it sit outside without a plug….. explains the seizure.

I let is sit over night with WD40 and tried to move the piston by the rear wheel in gear, no luck. The next day I decided to use a smoky-wrench. I got the barrel up to smoking and then applied some MBH (Mighty Big Hammer).

Actually it was a small hammer (until it connected with my left index finger…) and a long piece of wood. The pine stick eventually shattered so I switched to a steel pipe with a wooden puck on top of the piston.

After I got to BDC, I raised the barrel on wooden blocks and used a combination of pounding and at the very end turning the clutch with a oil wrench. The clutch was protected by a slice of old Norton inner tube.

The bore looks ok, some flaking at the very top and a 6mm strip missing between the exhaust ports, you can just see it in the video above. I figure there is no compression happening there anyway but concerned it may score the rings. I am hoping that I can get away without a re-chroming.

The piston looks ok, the rings are obviously gone! The crank has light rust and the big ends are tight, so I’ll have to crack the cases open and see what’s happening inside.

Alas, it looks like years of sitting under a deck with no spark-plug have taken their toll. I was hoping I could get away with a squirt of, squirt of gas and a good kick as I did with the ’66 250. I literally almost fell off the bike in shock and when it started on the third kick, yes started, not cough or sputter, but started!


fog machine

 

 

posted by Fastback in mechanical,Puch,restoration and have No Comments