Oil cooled engine number Conumdrum

[GS750E]

Hi Gents,

I Recently bought a project bike, A GS750E with an oil colled 750 engine fitted, bandit forks and GSXR swing arm. - it needs a lot of work.

The question I have is regarding the engine - it has the 749cc casting on the side of the barrels, but the engine number is PK34-******

I can't find anything on the web to tell me what year this is or what bike it even came from - I was told it was GSXR and assumed from the rear brake lever that it was a slabbie, but that now doesn't seem right unless it is an import?

Anyone come across this prefix before?

[Captain Chaos]

Welcome on OSS.

Looks like a Slingshot (cable clutch) 750 engine, 749cc and nipple on clutch cover says '90 or '91.

Valve adjusting with screws = '90

valve adjusting with shims = '91

But of course looks can be deceptive and it could be a Slabby engine with cable clutch conversion. Remove the camshaft cover and look at the valve adjusters and you'll know more.

[GS750E]

Thanks for the info Captain - though shouldn't the engine number be R7**?

The gear plate cover shows it as being a 6 speed - though this could of been changed, not had a chance to click through them yet.

[Gixer1460]

Not sure on this but 'virgin replacement cases' come unstamped, so that old scrap case number may be re-used. Possible that a race team had used 'new' cases and just stamped an identifying number for their purposes? What does the V5 say for engine number?

[Captain Chaos]

2 hours ago, GS750E said:

shouldn't the engine number be R7**?

yes.

[GS750E]

Got V5 back today and it lists a totally different number - possibly the old air cooled lump, no prefix quoted, but the number in the log book is 72876

 

[GS750E]

Slipping the cam cover off reveals no screw adjusters, so I assume adjustment is done by shims in the bucket above the valve stem - which makes it a 90 or later. 
happily the internals are looking clean and no appreciable wear on the cams. 

[Captain Chaos]

12 hours ago, GS750E said:

adjustment is done by shims in the bucket above the valve stem - which makes it a 90 or later. 

shim head is '91.

[GS750E]

I stand corrected, thanks Captain. Took the carbs off today and they are 38BSTs which is also 91 from what I can find, so it is all pointing to a 91, just can’t understand why the prefix isn’t R7**
there are 5 numbers after the PK34 which I wouldn’t of thought a race team would get as far as- surely they would start at 001 and go up from there a few engines a year?