Jawa 350 Oilmaster

[willatki]

Greetings from Canada!
 
Perhaps you can help me?
I now have an old Jawa 350 Oilmaster
[# 631-2-001511] without owner documents.
I need to know when it was manufactured.
Is there a list of serial numbers on the internet?
 
Bill

[Panzergranate]

If you have a single clock then the bike is a 1977 to 1988 model. The 1974 - 1976 models ran the Type 633 "Bizon" engine, which didn't have the slick shift clutch system fitted.

If you have the twin clocks, with the cigar shaped exhaust system and Type 631 engine, then it is a 1979 - 1981 Type 634-5-50 model.

There are only 7 variants of the JAWA Type 634, and bearing in mind the numbers produced, there are still a few million of them running somewhere on the planet.

Only one thing ever goes wrong with all JAWA engines from the Type 623/631/632/633/634 family and this is at 34,000 miles (or if the chain is run too tight), the gearbox final drive bearing wears and causes the top gear selector to ride the groove, wearing it away rapidly.

This manifests itself, to the rider, as the gearbox jumping out of top gear underload, then on the level and then not locking in at all. basicall 4th gear is useless.

Just spending $5 on a new selcetor and popping it in will see it chewed away within 50 miles.

The correct remedy os to replace the gearbox final drive sprocket bearing and the selector. Forkig out $20 for a brand new gear selector guide plate might be worthwhile on a 40,000 mile engine if the rivet has slop in it.

The Oilmaster actually holds a world record in that it has the highest amount of engine torque per cubic centimetre than any other internal combustion enegine ever built. (38 Pounds per Foot @ 3,800 RPM with just 343.23 cc!!)

Note that to rebuild the gearbox you DO NOT HAVE TO DRAIN THE GEAR OIL as the engine can have the right hand case removed and the gear cluster removes and loads as a cartridge system by simpy removing the guide rail pin. Always check this pin on a straight edge for signs of bending. They only cost $5 to replace anyway.

The engine shares a lot of maintainance ideas with JAWA Enduro bikes and I've actually had an engine out of a friend's bike, from when he stopped the bike, ger cluster out, changed the final drive sprocket bearing and put back together again, back in the bike and kicked into life in a timed 34 minutes. And just using the excellent standard issued bike tool kit!!

Apart from the CZ singles, this is the most mechanic friendly and easy to build engine you can find. Ideal for a beginner to play with. Even Homer Simpson could rebuild one!!

I've had several of these bikes but have now moved onto the late 1980's and 1990's Type 632 models with 12 Volt 228 Watt electrics.

Parts support is excelent for these bikes with many rd party manufacturers stepping in to make up the short fall.

Top speed is quoted at 86 MPH on leaded 20 to 24 % Toluene content gasoline. Fitting a K&N filter will see the speedo move past the 95 MPH mark,

Ferrodo and EBC make upgraded brake shoes for the brakes. This is highly adviseable, especially if you pull the engine power restrictor in the airbox (plastic tube in the plenum chamber!!)

Other mods are to replace the blotting paper in the airbox with spong foam sprayed in K&N filter oil. Makes starting and acceleration better.

The main jet should be a 115 though some are still found with the 92 running in jet. Some dealers, eh??!!

Pilot jet should be a 55 and should be between 1.25 and 1.5 turns out from fully screwed in.

Needle should be in the middle setting, though with the low energy unleaded gasoline, you might need to actually run it a notch lower.

If running on diesel/2 stroke oil mix (when gasoline isn't availabale) run it on the lowest lift setting. Top speed is usually only 80 MPH like this, but mine was hauling a sidecar as well.

The engine will also run on Methylated Spirits mixed with cooking oil and other bizzare concoctions. This was designed to be a millitary bike as well, you know.

Check out the MzB website for original and pattern spares for all JAWAs from the year dot.

Workshop manuals are available to be downloaded for ll JAWA models online. Best check out the JAWA CZ Owner's Club of Great Britain for JAWA related sites.

The year of manufacture is on the maker's plate on the headstock, along with other information. This is the same for all JAWAs ever built.

[willatki]

Thank you for the wealth of information!

Can you also tell me if draining the gas tank through the carburetor onto the ground when petcock in on position with engine not running is a standard feature of these velocipedes?  

(and how to correct this, other than being infallible in shutting the petcock?)

[Panzergranate]

Remove the carb, unscrew the float bowl cover and check that the float is actually fitted correctly.

The rod at the bottom of the float fits into a tube at the bottom of the float bowl. It is a common problem that ham fisted people will put the float in wrongly and this prevents it from working.

OK, if the float isn't in wrongly then check the float by shaking it. It should rattle because of the loose solder inside. If it doesn't rattle then it will probally have some gasoiline inside.

You need to heat it up with a blow torch and resolder the float seams.

The other thig to check, on all floats in any carb, is the pintle valve seat and the needle on top of the float (the pintle).

The point should not have a ridge worn onto it. If it has use a Swiss File to file it flat and shape the point.

Check ot the float chamber lid top to see if the valve seat is damaged or full of dirt or fuel additive residue.

Whilst the carb is off give it s good clean out of all the powder residue that modern fuel leaves behind. Use a carb cleaner aerosol.

If you dismantle the airbox on an Oilmaster you'll find a plastic pipe in the Plenum chamber, behind the carb. Remove the thing as it restricts and loads up the carb's airflow at higher engine speeds. It is there to comply with Austrian engine capacity power output restrictions.

350cc bikes are not allowed to make more than 27 to 28 BHP in Austria.

If you fit a K&N filter straight onto the carb, lift the needle one notch, thus bypassing the airbox, the bike will push past 90 MPH when in good order.

Points settings are 2.8mm. BTDC. The points timing is more essential than the points gap, which is basically so that you can have a reference point for quick timing checks.

You set the timing first and then fiddle the mounting plate position of the right hand cylinder until both the timing of 2.8mm. and gap of 0.14" at TDC match.

Then repeat the whole thing with the left hand cylinder and half plate.

The ring gap should be way below 0.8mm. If it is more than this, they'll need replacing.

To check the coils you can used the traditional HOTTAS method. You'll need an assistant for this.

Say to the assistant, "Hold On To This A Second", and hand the assistant the end of the coil's spark plug lead.

Next trip the points with the ignition on and evaluate the assistant's reaction. Coil strength can be graded as follows.:-

No reaction = Coil dead!!

"Ow" = Weak Coil.

"F**king hell" = Good Coil.

Assistant jumps a good distance and lays twitching on the floor = Racing Coil.

This procedure is totally safe as only the assistant suffers, not you!!

It is best advised, for post test safety to make sure that there are no ready to hand objects that could be hurled at you in close proximity to the assistant. Also ensure that your  escape options are clear.

I used to use my younger brother for this and could use him at least twice a day for this test. He isn't the sharpest tool in the box, at times.

[willatki]

Thanks for the carb info and love the HOTTAS test!

[Panzergranate]

I had a youngster hanging around the gang, back in the 1980's always after freebie repairs.

Anyway, one November day, he asked about how to prevent bad starting in cold weather.

Always quick to spot an oportunity for a good wind up, I told him that it was possible to buy a can of Spray On Anti-Freeze For Aircooled Engined. The stuff was intended to be sprayed all over the fins and it would prevent rapid heat loss. I also told him that as his engine was black, he should ask for the black engine spray, not the silver.

So I sent him off to Huxhams and told him to say that I'd sent him.

I was told what they did when he arrived when I visited them a few days later. What happended was that he turned up and asked for the Spray On Anti-Freeze For Black Finned Air Coolded Engines.

So they went into the store room, made lots of nise like they were hunting around for it, and then came out and told him that they'd sold out of the black cans, but still had silver in stock. They told him thta black was a popular colour.

They sent him over to Cresent Motorcycles in Charminster, Bournemouth and phoned ahead to tell them the details of the wind up.

Aparently Cresents then sent him over to Barclays Motorcycles in Boscome. Phil Meech still remembers this wind up even after 20 years!! Anyway, from there he was sent to Ray Fishers in Christchurch, and after that the trail goes cold. However, he aparently trapsed around 20 motorcycle dealers and covered 30 miles or more looking for a can of Spray On Anti-Freeze For Black Finned Engines. That was what he told me the following week.

He claimed, quote, "I tried everywhere, but eveyone only had silver left!!"

And then there was the recent one, last year, when I sent a couple of kids off around the dealers asking for a carb balancing spirit level so that they could balance they're rubber mounted single cylinder and carbed.

Of course I said to tell them who sent them, etc.

Youngsters today are just so niave and gulible.

[Tinker]

I found the market for Honda's CB400A!  Ship'em to Austria, and replace the 400 decals with 350 decals!

[myljach]

offtopic: anybody wish buy Jawa speedway 500 ccm, OHC valves?