GS450S Wont rev

[Guest]

OK, so I just rebuilt the carbs, all new 'O' Rings and gaskets, (Thanks Bob)screws all re-plated and the carb bodies ultrasonically cleaned and bodies vapour blasted.

All good so far, they look like new , bolted them onto the bike (minus fuel tank) but filled them up to try out the bike. Bike started almost immediately and after a little fine tuning due to high tickover the bike seemed fine.. till you try and rev it.. just dies.

Airbox pulled back, engine running, throttle slides dont lift .. ah ha.. twist throttle slowly and they 'butterfly' a little.. but dont rise..

before I tear down again, any one think I've missed anything silly..

Thanks all

[Nessism]

So airbox installed, filter in place and properly oiled, top cover installed and sealed? Stock exhaust? Jetting all stock? Any modifications to the stock system can result in the problem you mention.

[Showtime]

Airbox is on, but minus top cover and filter, bike is stock, no mods at all, just wanted to run it up before I replaced everything else.

will not pick up at all on the throttle, but ticks over beautifully..

[Big Rich]

Is the vacuum line to the carbs plugged since it isn't hooked up to the petcock? And if you pull the airbox back to see what the carbs are doing, they react differently than if the airbox is installed.

[tkent02]

Airbox is on, but minus top cover and filter,

Try it with the filter and top cover installed, it may just run fine.

These things are that sensitive to intake restrictions, or lack of.

[Showtime]

Pics added

Thanks for the input guys, I hadn't plugged the vacuum intake and are you saying the carbs are that sensitive a sealed airbox is a must.. Appreciate the input, Not worked on these carbs before, but with (what I thought) was a thorough job of cleaning and preparation was sure they would be OK.

Pics below of the carbs in current state and how the bike is right now (No airbox lid , vacuum unplugged etc..) Am I wrong to assume bike will run OK like this..

[tkent02]

Don't know much about the twins, I have one but haven't put it together yet. On the fours with CV carbs that would make it run terrible, might idle but it wouldn't be able to rev up. Try closing off most of the air box intake, like 90% of the hole. Or fold a rag or towel and hold it over the hole. It might run better. Get the right aount of restriction and it will run fairly well, but with the filter put together correctly it will run great at all RPMs.

Your carburetors look great by the way.

[Showtime]

Don't know much about the twins, I have one but haven't put it together yet. On the fours with CV carbs that would make it run terrible, might idle but it wouldn't be able to rev up. Try closing off most of the air box intake, like 90% of the hole. Or fold a rag or towel and hold it over the hole. It might run better. Get the right aount of restriction and it will run fairly well, but with the filter put together correctly it will run great at all RPMs.

Your carburetors look great by the way.

Thanks TKent01 for the input, I'll excercise restraint at this point, There was no filter at all with the bike, so I'll get one, and seal everything as it should be and see after that. Thanks for the heads up on the carbs.. took a lot of work to get them like that.. all original screws and brackets/levers, I just used a benchtop grit blaster (Glass beads) and then ran them all through a home plating kit.. results are superb. Really happy with them..

Once it's running right I'll set to the rest of it, but didn't want to disturb too much till it was going.

[Showtime]

Revving but not cleanly

OK, quick update on the 450. Carbs back on, vacuum plugged, airbox on, new oiled filter, cap on airbox.

Bike now revs as long as choke is on... turn off choke.. just dies, wont rev..

what a frustrating bike.. any ideas as to what now..

[Nessism]

How much warm up time are you giving it? GS's won't run cleanly without choke until the engine is up to operating temp (or close). Also, have you vacuum synced the carbs and set the pilot screws to about 3 turns open?

[JTGS850GL]

Also, you need to make sure the main idle screws is set to about 3 turns in as a staring point.