GS750 needs more umph

[THUNDERPIPES]

I am new to GS Resource and this is my first posting, so hello to you all. My trusted GS750DB(1977)is now in need of replacement pistons & rings due to a drop in compression , excessive oil consumption and also being thrashed for 34years! I have been told that the GS850 top end will fit and offer more umph!!!. Also i am told that the GS1000 camshafts fit in place of the GS850`s giving better gas flow.The bike benefits a Harris 4 into 1 exhaust. My intention is to also install K&N air filters and GS850 main jets to the carbs.
I am keen to here from anyone with useful advise and tips or cheap parts, or has undertaken a similar task. Kind Regards William.

 

[yank]

Welcome, How many miles,have you done any maintenance,has the bike ever had any maintenance? Low comprehension could be the valves are out of adjustment.Welcome again,others will be along.ooppss Compression ,I must have had a low comprehension moment.

 

[Allie]

Caint help ye much in the tech dept, but I can offer you a big welcome! (not big compared to the one that's coming though...)

I've heard that if you want a faster motorcycle the cheapest way to get one is to go buy one that's already faster. That said, since yours needs refreshing anyway those mods you spoke of have been used by others here and aren't that radical, they should be able to offer you all the insight you need on that front. I'd be surprised to learn that stock 850 jets will suffice for the setup you have in mind though.

P.S. the GS750 is the best bike in the world... got any pics?

 

[Nessism]

You can install the 850 cylinders and pistons. The 1979 850 head is same as yours, but you could install a later 850 head, the kind that take CV carbs, because the intake ports are larger which will breath better if you upgraded the carbs to something bigger. The 1000 cams will fit, but the 750 cams are hotter already (more duration) so that won't help you any.

 

[keman]

Before you go to the drastic measure of major work, adjust your valves. The valves on these bikes get tighter with time, and can cause loss of compression due to the valve no longer closing fully.
click the link in my Sig for a mass of information on how to, and what to do...

 

[THUNDERPIPES]

wow-this is a great site..!!!

wow-this is a great site..!!!

Wow- i`m overwhelmed by the response from my first posting, thank you.This is exactly what i was hoping to find. Brilliant. Still trying to navigate the site so please bare with me.

 

[Allie]

Always assuming, of course, that he hasn't touched his valves in 34 years.

 

[THUNDERPIPES]

Gs750db

Gs750db

Welcome, How many miles,have you done any maintenance,has the bike ever had any maintenance? Low comprehension could be the valves are out of adjustment.Welcome again,others will be along.

Hi yank, thank you for your message.the clocks show just 22,000 miles ,however it has been park in a garage for several years rusting away. I shall take your wise advise and check the valve clearances before stripping down. kind Regards William.

 

[Guest]

The 79 GS850 has the same main jets as the 750. You will need to rejet your carbs for the pipe and pods more than the increase of CC's.

The 850 cylinders and pistons do effectively "bolt-on"; however in my case the cylinder sleeves hit the inside of the cases with about 10mm to go. It was simply a matter of scraping/grinding a little of the aluminium case at those points - not as drastic as it sounds and only a fraction of the time involved for the overall job.

Research a lot on this site before you go ahead and you'll be fine.

Replace your valve stem seals whilst your in there too! And don't skimp on the head gasket - go Suzuki OEM for this.

 

[bccap]

Welcome. I haven't seen that many 77's posted on this site. { none that I recall } Which makes me wonder. Are there any 76's out there ? Also we like pics. Lots and lots of pics !

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. THUNDERPIPES,

With 22K miles, your GS is barely past break-in. It really shouldn't need a top end refresh unless it has been severely neglected. Check all the items in the maintenance lists in your "mega-welcome". You have a 30 year old bike that needs 20 years worth of maintenance. You might be surprised how it behaves once you have given it some TLC and brought it back to its former glory, a safe and reliable condition.

Let me dump a TON if information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

 

[Guest]

Get an 1100!

 

[Nessism]

Adjust the valves...although it may be too late.

 

[dardoonk]

Welcome. I haven't seen that many 77's posted on this site. { none that I recall } Which makes me wonder. Are there any 76's out there ? Also we like pics. Lots and lots of pics !

Here's your first look at a 77 on this site, bccap...

 

[allojohn]

Here's your first look at a 77 on this site, bccap...

That's a very pleasant machine you have there Dardoonk.

 

[BigD_83]

Here's your first look at a 77 on this site, bccap...

Me likey your '77....very much. Great look, nice lines. What's the swingarm from, and I assume the fork and front brakes are not stock?

Now, back to those valves...

 

[bccap]

Great looking bike dardoonk ! I like the color scheme.

 

[1948man]

Hi yank, thank you for your message.the clocks show just 22,000 miles ,however it has been park in a garage for several years rusting away. I shall take your wise advise and check the valve clearances before stripping down. kind Regards William.

When get the valves adjusted, just riding it hard for a thousand miles may restore some compression. It's worth a try before you do a transplant.

 

[dardoonk]

Me likey your '77....very much. Great look, nice lines. What's the swingarm from, and I assume the fork and front brakes are not stock?

Now, back to those valves...

Front end components & swinger are lifted off an 83 GS1100E.

 

[hampshirehog]

Hello William and welcome aboard the good ship GSR. A few lads from Kent on here - all within a stone's throw of Robinsons so you don't have to rely on the postman.

You can't go wrong with an 8 valve 750 - unbustable. If she's only got 22k on there she probably only needs a bit of basic maintenance and a bloody good thrash to sort her out. Valve check is an absolute must - she could have made it this far without the clearances ever having been done and that's why she's looking down on compression. Have you done a compression test by the way - hot engine and WOT? And the oil smoke might just be caused by hardened valve stem oil seals. Does she run cleaner when she's warmed up?

For added pep the 1979 850 top end bolts straight on, 1980 onwards needs a bit more work but not much. Leave the 750 cams in there - they are mildly hotter (exhaust has a tad more duration) than the 850 and the 1000.