engine help - best options please

[jasonexup]

Need some advice on best ways forward while I'm sat by the side of the road with a puddle of under my 750!!!!

There was a little smoke from the left can on start up that cleared, left it warming up and set off. Three miles in, clouds of smoke from both pipes and big oil loss with no obvious untoward noises. All suggestions/answers/options welcomed as we are booked on a crossing to France early August so I need to resolve quite quickly.

1 - Can the head be removed with engine in?

2 - How likely is it to be head gasket/top end only?

If this us not an option I have an 1100 engine, carbs and headers. I know I will need front engine mounts...anything else, CDI I guess.. anyone have these?

Failing this, does anyone have a good used 750 motor available? Or anyone rebuild mine in a short timescale (obviously for money).

HELP!!!!*

Thanks for reading ...Jason

[Pop-Kat]

As far as I know the cdi units are the same for 750 and 1100. the engine mounts you need are under the engine either side, you could knock them up in an afternoon once the engines fitted, very simple triangle with 3 holes. gearing might be out, so you might need sprockets. I'd advise doing a compression test on the 1100 engine before fitting it.
As for your 750, pretty much impossible to diagnose here, but a bit more info might help. Where was the oil coming from ?

[jasonexup]

Hi all the oil came out of the exhausts... No external signs of leaking at all.

Thanks for your response...

[Pop-Kat]

Think you need to pull the top off and investigate, sounds like a holed piston but you'd have no compression then, could be head gasket but that's a big gasket failure. the 1100 top end comes off in the frame so the 750 should come off easily. good luck with it and post up what you find.

[jasonexup]

That's helpful at least I know where to start...I really suspect it's top end so it's worth taking the head off to see how the land lies....

I will compression test the 1100 before fitting if that's the best route....

Thanks Malc

[sparki]

If you replace the only things you'll need are lower engine mounts and maybe a set of 34 or 36mm carbs as the GS75 motors only had 32's on them afaik. Ignition and wiring are the same ... Bar the oil pressure wire. On a 750 it's off the oil filter cover... The 1100 is below the cam chain tensioner...

Check the 750 first but if damaged pull it out, do a compression test on the 1100 and shove that in with a bigger set of carbs... Job done

Depending on which 750 will determine size of back wheel but tbh the worst will be its a little long and that's it.... No need to change chain or sprockets if they're in good nick and will hardly be noticeable

If the 750 motor is scrap remove the oil pump gears from it as they are worth more second hand than the entire 750 lump is in running condition...

Oh.... And are you not interested in this free top box as I haven't heard anything back from t he pm I sent some time back now?

[Pedda]

Once your on it with a comptest on the 1100, you should also do it on the 7.5.
Did the 7.5 engine stand around for a longer time without running?
I'd check valve seals first, might also be piston rings.

If the 1100 is a runner, implantin it would be the easiest fix.

[jasonexup]

Sparki...Thanks for info, I'll PM you on top box.

Pedda...I think it may have stood for a couple of years without running, so I guess the valve stem oil seals may have hardened or a piston ring stuck then cracked?

Thanks to all, Jason

[fossie]

How we getting Jason, I ask cos I know you are supposed to be taking it away on your jollies in a few weeks.

I would ask does it start ok? Run. Ok. Only because as a cheap skate I look for the easiest explanation . I had a I bike that had similar issues but it was just someone had filled the zorsts with oil to preserve them!

Or have you sourced some carbs for an 1100.

I have a 750 engine here but. Completely unknown. And has been stood, but we could pour diesel down the bores to free them. And check compression.
You could come up or I will bring it down when I pick up the t shirts, Which I will pay the deposit for today and total on the 11 th when I collect the shirts.

[jasonexup]

Thanks for the offer Fossie....this is where I'm at gents....I now an 1100 engine sat in the frame wired up. The 750 engine showed on compression test:

1-115psi
2-20psi
3-75psi
4-110psi

Hence the 1100 engine being fitted.

The 1100 came with carbs and a 4-1 with a laser can. I've just had such a bitch trying to get the airbox / carbs lined up that I'm having a break....I just checked the main jets and they are 160 which sounds huge to me!!! I can only only guess it had pod filters with the 4-1 to need such jets so as a dirty fix til winter I'm going to put K&N/Ramair filters and see how it runs.

Any thoughts on the main jet size/running pods and 4-1 at 160?