Bike doesnt return to low rpm and camchaintensioner is moving

[Teun]

So i got a beautiful gs 400 from 1977 as a gift that had been sitting for over 15 years. I got it running again, cleaned the carbs and some other minor fixes. It idles fine but when i'm riding and close the throttle the rpms dont return to normal. The only way to lower the rpm is to stop and slowly open up the clutch. I suspect a vacuum leak somewhere. Am i right? i hope not because the rubber parts are a **** to come by in the Netherlands especially the ones that go from airbox to carb.

The Camchain tensioner also moves, i already took it off the bike to reset it and wound up the big spring an extra turn, but it still moves.

This is my first dive in the world of motorcycle repair so I am kind of clueless on what to do next so I hope you guys can lend me some of your knowledge.

[Rich82GS750TZ]

Unless your throttle cable or throttle linkage on the carbs are sticking, your rev hang is likely due to air leaks in front of and/or behind the carbs. Sorry.

The cam chain tensioner is supposed to move. At least bounce a tiny bit while the bike is running. That’s its job. Not sure winding the knob an extra turn is best practice. Maybe take a look at the tensioner rebuild tutorials on BikeCliffs website, linked in my signature.

Welcome to the site, and to the wonderful, fun world of vintage motorcycles.

[tom203]

You don’t sound that clueless....camchain tensioner fools a lot of folks during reinstall...make sure you do it right

http://members.dslextreme.com/users/storagecliff/images/engine_odds-n-ends.html#A06

[Redman]

For intake air leak, maybe you need just the o-rings (that are up against the head).

When get o-rings also get another set of bolts-screws for the boots because likely to destroy some of them Getting them out.

Maybe check with “cycle o-rings” (a fine member here) to see if he does international shipping.

[Teun]

Thanks for all the helpfull replies. I am going to order some new parts and hopefully that solves it because i really want to ride this beautiful bike.

[BigD_83]

Am i right? i hope not because the rubber parts are a **** to come by in the Netherlands especially the ones that go from airbox to carb.

Aren't these guys still around?

https://www.cmsnl.com/

[Hokano12]

Yes, many of my friends in japan use that site to buy oem Suzuki parts.

[fastbysuzuki]

Or maybe these guys. https://www.motorcyclespareparts.eu/en

[Wheelies]

I had something like this on a BMW R100,it turned out to be the timing back plate had moved during rebuild and the timing was way too advanced