1976 175 cross country nightmare

recently bought it out of the Dwight Rudder/Lee Clark museum .100 point bike,
WILL NOT KICK START.pull off only and not easily then
good spark, timing at 1.4mm btdc . pulled and put carb on an ossa sdr and it cranked second kickand purs like a kitten.
hear spark knock at high rpm which makes no sence to me with such retarded timing.premium
only way it will idle is with idle screw bottomed out .(timing may explain)
160 psi cylinder pressure
top end new,pipe clean

in my 60s and really try hard to keep my bikes crarking easily.
any help for the new old guy will be greatly appeciated.
always said if it had compression i could make it run
now
the nicesest bike i oun and 1st Husky
has stumped and humbled me
please help thanks
Hawk

What does the plug look like after attempting to start it?
Any chance the lower end is fouled with fuel?

Frame an MK or ML? Manual says MK at 1.43mm BTDC ML says 2.13MM BTDC don't know why the difference same engine I think. Also one uses a 34mm Amal and one a 32mm Amal and differnt jetting. Also I don't think 100 point museum bikes were built to actually run LOL!

If I understand you correctly, it WILL start pulling it down the road and friction starting, correct? I would check that your intake boot isn't deteriorated and cracked, letting in air. The other possibility would be the crank seals have dried out through years of being a showroom bike...also allowing air to be drawn in when trying to start and seriously leaning out the mixture. When you have managed to get it to start, what does the plug look look like afterwords?
As to the timing, it should start and run just fine even if somewhat retarded.

The clues are... idles with the idle screw right in and knocking at high revs... smacks of a crankcase seal or a blocked exhaust.. no wasp nests in there is there? also check the carb vent holes no you've done that it runs on the Ossa.... spray wd 40 around the seals as you turn it over and look for bubbles.

thanks guys
been out of town this week

appreciate the responces
heres a little more info
its an ML,mag motor Burlison sdr bike
100 point is probably ambitious buy some number
just trying to say that mechanically and cosmetically, it was very well done down to the small
details . its a much nicer than the other 1dozen bikes that i own,ride , and fall off of almost daily
which FWIW include for this discussion a
1973 175 ossa sdr
1973 250 ossa sdr
1972 125 DKW Hercules isdt
2 1974 Bultaco Matador SD,s
1970 250 Bultaco Matador
1973 cz 250 red tank isdt conversion
1968 Penton 125 isdt steel tanker
i can keep all of these cranking easily and running properly
that said


i found a dealer service bulletin ,dated late 1975 i think that said back timing to 1.4 to 1.5 and rejet from the factory 220 and 3/4 turn to 290 and 1 and 1/2 . seems all the early bikes siezed running too lean, even found a recall for a piston upgrade to help the same problem
am understanding now i guess why the 175mag lasted only 2 years
found that the carb had indeed been jetted properly and timing was correct(tried 2.3 ,2.1, 1.9 1.7 and 1.5 also
i obviously suspected an air leak from the start so i checked reed valve manifold and changed the crankshaft seal (which looked perfect though but i happened to have one on the shelf anyhow)
had the cylinder off ,piston new 1st over,cleaned exhaust pipe
even swapped the motoplat from of Rudders 250s
im to the point of returning it to its previous home
but
i really would like to figure this out
i am at wits end

Sorry to zombify this thread but I happened to stumble across it and thought I would provide some more info for anyone else who might find it later on. Since it was 2 1/2 years ago that the question was originally posed, I assume youngblood has either figured out the answer by now or given up and gotten rid of the bike.

But here goes anyway. If Mick’s posted timing specs are correct (I haven’t checked, but have no reason to believe they aren’t) then the answer is pretty obvious - youngblood was using the wrong timing for his engine. The ML and MK framed 175s used two completely different engines, which is why the timing specs are different. I know because I owned one of each. Still do, in fact. (Although both are in various states of disassembly now.) The pre-ML bikes used a 125CR/WR engine with a re-sleeved cylinder and larger diameter piston. In fact, the owner of a pre-ML 125 could turn his bike into a 175 by simply buying the 175 cylinder/piston kit, which was available separately and consisted of a larger bore cylinder and larger diameter piston and ring. That is what I did at the time, transforming my 1974 Husky 125WR into a 175WR. The 175 cylinder bore was larger, but the stroke was the same.

In contrast, the ML framed 175GP, which originally came out in 1975, used a completely new engine and cylinder - hence the different timing. The ML bikes also used a reed valve as stock, which the earlier 125/175 did not.

So there’s the primary answer to why things didn’t run right, although there may have been other issues too, such as a possible air leak. But the main issue seems to be youngblood using the MK timing specs on the engine of an ML bike. So it wasn’t likely to run very well.

nothing wrong with your post..valuable info for posterities sake! hopefully it will help someone in the future