750 oil pump

Paul Marx

Paul Marx

Hero member
Location
France
Hi all,

I've just changed the twin primary chains on my SF to put in one of Andy's duplex chains.
The oil pump drive shaft is extremely tight in the pump body, by extremely I mean that it can't be turned by hand. It was always tight, I remember from last time I changed the primaries, but not to that extent. After a lot of messing about, 2 hours of heat and swearing and my girlfreind being pissed off,, I managed to get the gear and shaft out. It turns out that there is a small burr in the pump body binding the shaft where the key enters the keyway on the inside of the body, a left over from a previous extraction no doubt. Even without the burr, the shaft is very tight. I've looked at the way the pump functions and apparently there's absolutely no risk of loss of oil pressure if I slightly relieve the bore in the pump body with a bit of wett and dry.

Can someone confirm?

Thanks
Ciao
Paul
 
Go ahead Paul. 

Won't do any harm, just make sure all traces of abrasives are removed before you stuff it back together.

Have you tried "bumping" the pump body around a bit?  There's usually a sweet spot to be found somewhere.

piet
 
Have you tried "bumping" the pump body around a bit?  There's usually a sweet spot to be found somewhere.
Click to expand...
As the pump body tends to move whenever tightening the screws (and so
causing binds)I use a shaft the same dia. as the drive shaft (afair 12mm)to
fix the pump body's position during tightening. Helps a lot.
Had some problems with aftermarket 10mm pumps turning very hard. Turned
out that the gears were a little bit too "thick". Grinded them down on a glass
plate with abrasive paper.

Ernesto
 
Thanks for your answers confirming what I thought.
As for bumping Piet, the shaft binds in the pump body off the case.

Ernesto, your use of a dowel shaft to locate the pump when tightening is excelent.

Ciao a tutti
Paul
 
Ok, eased off the bore of the shaft and the gear spins freely. As soon as I tighten the pump to the crankcase, the gear shaft goes in quite easily which it didn't before but it's quite impossible to turn the pump gears over by hand. Even if I use a shaft to center the pump.
What's up?
Could be the pump gears being a bit proud by eye, but then that engine has about 80 000 km.
Any ideas?

Ciao
Paul
 
i wouldn't think the gears proud as the body and case would wear before the gears
but certainly worth checking

look on the case for any proud bits around screw threads
also any burrs in case material or pump body
look to the drive pin in the shaft for any burrs that may cause the gear to be cocked

the pump body isn't very stiff so its best to progressively tighten the screws

cheers,
scott
 
Thanks Scott.
I'll double check everything. The inside of the pump is in excelent condition with no wear or score marks. It may simply be that I'm tightening the screws to much? Pump turns freely with screws just nipped up. I always tighten progressively in a cross pattern and then punch the screw heads. I do up the screws really tight for peace of mind but maybe less tight with a bit of Loctite locking fluid on the threads would do it.
It's the first time since I rebuilt the engine in 91 that I've had that pump off to investigate why it was so stiff, but I remember it being very stiff last time I changed the primaries maybe 10 years back! I'm getting to be more of a perfectionist as I get older, can't be bad!

Cheers
Paul
 
Paul,

While gradually tightening and your guide shaft inserted, bump the body around a little.  A gentle tap sideways on the shaft is normally enough to shift it.

When fitting pumps, I only use 2 screws inserted diagonally initially to work out where the sweet spot is.  When all is free and easy, I insert the other two without disrupting the tightened ones.  A bit of patience is sometimes needed, but it eventually works out ok.

piet
 
All sorted, just one of those very annoying mechanical setbacks where something which should take a few minutes ends up taking hours.

It turns out that I hadn't sanded back enough a small burr at the inner entrance to the keyway, leaving the driving gear slightly proud and therefore binding against the crankcase when the pump was tightened down.
3 seconds with a Dremel and Bob's your uncle!

As I mentionned earlier, I noticed that the pump was stiff when I rebuilt the engine back in 91. Memory has come flooding back and in fact that SF2 engine had stripped a tooth from the large pump/ignition driving gear when I first opened it so the stiff pump was probably a factory feature. The later bikes had fine teeth and a different number of teeth therefore than the earlier ones. I remplaced that gear and the crank gear with a large tooth GT set which I had spare back in 91; that's what's still in there 80 000 km later.

I'll now be able to finish my simple primary chain change, check engine settings and have the bike ready for next weekends british bike rally! Must keep the flag flying.

Ciao a tutti
Paul
 
Hi Ernesto,

I also put the roller primary tensionner and the peg clutch back in my S. Anorak anybody?

To cut a long story short, in 86 or 87, I picked up a pair of 750s for next to nothing: an early GT and an SF2. Both were pretty miserable and missing parts.
The SF2 was the easiest to restore so I did that one first, still haven't got round to doing the GT, I'll be retiring if all goes well in 5 years time and have my work cut out.
I managed to find the missing parts for the SF2 at my local dealers, the good old days ( I later bought all the stock he had left): starter motor and freewheel, front mudguard, exhaust down pipes notably.
I stripped the engine, it being an unknown quantity and for the fun. The bike had 20 000 km on the clocks. I found scuffing on one of the pistons due no doubt to hasty running in, that piston is still in there, and a missing tooth on the oil pump/ignition driving gear. So I plundered the GT for those parts which are still in there as well.
Bike was back on the road early 92 and has had no major work since apart from the bronze bush on a layshaft gear which quite literaly disappeared which I think was the consequence of a rally we did in Paris involving three or four hours stuck in an enormous traffic jam which I think fried the bush!

Ciao
Paul

 

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It's been a case of never think things are going to go smoothly, sometimes they do, and sometimes, not.
I'd planned a winter program for the SF2 with a do by date of March 24-25th since I have a rally that weekend.
Change oil, change primary chain, look into swingarm bearings, fabricate  a mounting for twin Fiam horns and wire them in, change slides, needles and needle jets, oil cables etc.
About six weeks ago, it was time to stop messing about with the race bike and get to work.
I dismantle the primary case to find the clutch moving around about 3mm on the mainshaft. I had to dismantle it anyway since I couldn't get Andys Merc. chain on there by just slipping the cluch sprocket off. I found that the bronze bush was totaly shot, ovalised and spilt! Time for a change. Since I have no easy access to machinig facilities, I order an oversize bush from Andy Wagner after having measured everything up, roughly.
When I got the bush, no way, it was floating around in the clutch, I would have needed to machine the clutch and make up an oversize bush.
So I dove in to my stash of parts and got another clutch. While I was at it, I thought I'd get the rivets out, tap and put screws in making things easier next time I was in ther. Of course I didn't read the advice of people who do this regularly, ie drill off the rivet heads on the inside and push out from there after heating. I ground off the other side and pushed through from there. Of course, I managed to split two spring posts but that's more of personnal insatisfaction than a mechanical risk. So, cluch ok and then the problem with the oil pump. That set me back another week!

It's all back together now. Timing needs setting, tension cam chain and do tappets, change slides, needles and needle jets. Will at last be done this weekend. Do 50 km and off for the british bike rally in a week.

After that, into swingarm and mount horns.

Then change primary and secondary chains on the Electronica, I have a track day on May 27th.
Then back to the race bike so as to get it out and run it in this summer.

Ciao a tutti
Paul

 

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Paul,

Don't chuck the knackered clutch basket in the skip, can be reclaimed with the needle bearing set-up as used in the triples.  The bearing cages are a bit larger than the bush, 10 lathe minutes gets you back in business.

If you can't find anybody willing to tackle it, postage to Germany can't be that high... :D

piet

 
Thanks for the offer Piet, I may well take it up, and don't worry, I don't throw any parts in the skip, however knackered they appear.
Paul
 
After that, into swingarm and mount horns.
Click to expand...
Hi, Paul.
Concerning the horn mount: be sure to use the original
elastic package of sheet metal. A stiff stripe of metal
won't survive the vibrations, guess how I know.
PN for the package is 21 118 023

Ernesto
 
Hi Ernesto,

We exchanged on the horn mounting already some time ago since I intended making an aluminium bracket. I may still do that, my intention being to use several superimposed strips of aly to reduce harmonic effect!
Then again, I may not.

In any case, after having lost a few horns, they are now lockwired so that if the bracket breaks, the horn will stay dangling there.

Ciao
Paul
 
Paul Marx said:
Hi Ernesto,

I also put the roller primary tensionner and the peg clutch back in my S. Anorak anybody?
Click to expand...
Hi Paul, I also hope to keep the original peg clutch in my 'S' can I ask what springs you used please?

Thanks Norman
p.s. I'm also keeping the roller primary tensioner - never gave any trouble on that GT I had and that did a few hard miles.
 
Hi Norman,
I can't remember about the springs. Aren't they the same reference whatever the clutch? I probably got the new springs from Toddy.
Paul
 
All working fine apparently. Did about 20 km this afternoon, the last 4 or 5 at 140 kph. Bike running sweetly, obviously needed a quick carb tune after having changed slides, needles, needle jets.
It's nice to hear that chain whine after the clunking of the worn twin primary chains and clutch hub.

A lot of work is nearing completion: fork oil done, brake fluid changed, instrument holder repaired again, broken at the front mount of course. The strap holding the under engine exhaust crossover had disappeared. Oil changed, primary chain done, clutch repaired and of course, timing, cam chain tension and tappets done. Swing arm bearings, twin horn mounting and rear brake to come after next weekends rally.

It's strange getting seriously back into a machine I restored over 20 years back. Eyes and hands seem not to have seen time go by and memory brings pictures flooding back like the use of those early timing/oil pump gears.
It's also the time when you realise, at least I did that many times I just thought "that'll do", but twenty years on with a machine nearly 40 years old, some approximate work is showing up it's failings. The clutch hub is one example. I'd changed the bronze bush last time around, I had a new one to hand. The new bush wasn't nice and tight in the hub. I thought "that'll do". 15 or 20 000 km later, it doesn't do any more.

Another thing I've been ignoring for years is the tappet cover studs. I originaly used domed nuts to tighten down the covers, nice looking, only they tend to bottom when you do them up tight, at least these did, damaging the threads. I've since replaced them with ordinary nuts. I've known each time I set the tappets over the last few years that the day would come when I'd have to change those studs. This time, I really thought that I wouldn't be able to tighten the covers down. I managed to reclaim the threads sufficently but it'll be the last time.
Next winter, change the 8 studs.

Ciao
Paul
 
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