Now that it's starting, it only runs with choke

[Guest]

so the starting problem was because of reversed coils.
carbs are clean,new o-rings in the carbs and in the intake
unifilter pods,no mufflers at the moment.
afaik main jets are 120,pilots are 42.5
pilot screws 2 1/2 turns out
it starts with the choke pulled all the way, after a minute i can push the choke a little bit back and the rpm will rise. if i push the choke further back it dies.
while choke is pulled it will response to the throttle. but not very smoothly
to my understanding it's running lean, i know i need to rejet the mains because of the pods,but do they effect idle? same question regarding the needle, is changing needle height can help with idle too?
also, how to check if i have intake leaks?

Thanks for all the great help i'm getting here, i couldn't have get this far with the bike without it :-)

Eran

[allojohn]

No muffler??

With no back pressure I wouldn't expect it to run very well either- choke or no!

[Steve]

Try turning the idle speed screw in about one turn.

Activating the "choke" opens alternate air and fuel passages, so idle speed setting is somewhat irrelevant.

.

[Maddevill]

Idle jets are for idle to 1/4 throttle, slide needle is for 1/4 to 3/4 throttle, main jet is for 3/4 throttle to open. All these jets overlap function as well to some extent. You know you are super lean right now due to it's running better with a lot of choke. Might as well start re-jetting it, but you really need the mufflers or a pipe on to get it close.

[spyug]

Sounds like a few issues including perhaps intake leaks causing an over lean situation. The easiest way to check is to spray either Quick Start (ether) or WD40 or other penetrating fluid around the intake boots with the bike running. If the bike revs or alternatively dies you have leaky carb boot O-rings.

As also mentioned, without mufflers it is not going to have sufficient back pressure and will not run right. The pod filters are not helping either. Unis are good filters but do you have them properly oiled? If not they will not be sufficiently restrictive and as you noted, the carbs need to be rejetted to compensate as well.

You definitely have a few issues to consider. Perhaps start by checking for airleaks and also "fatten up" your jets to at least the next sizes up. Make sure your filters are oiled too. It should start to run better but then, of course, you will need to put on some mufflers as also mentioned.

As Steve mentions, until you get it running without choke trying to get it to idle is a waste of time. Before you get to that even you should also balance the carbs. but we are getting way ahead of ourselves.

Get it to at least run without choke first.

Good luck.

[eran_k]

I learn new things every day! noted and will get done.
I will put the mufflers on tomorrow, although they are quit minimal (short slush cut units)
I will order some jets and will oil the filters and check for leaks.
should i get also bigger pilot jets?

Eran

[Johno]

Do you have a vacuum operated petcock?

Is it correctly attached or blocked if you are using a temporary fuel tank?

[Steve]

should i get also bigger pilot jets?

Usually, that is not necessary.

Although re-jetting is necessary for pods and pipes, that is only necessary due to the extra air than can flow, due to less restriction imposed by the stock airbox and the mufflers. However, at less-than-full throttle settings, it is the throttle mechansim (slides in the VM carbs, butterflies in the BS carbs) that causes the restriction, so the carbs don't flow any more air at idle, regardless of what is upstream or downstream.

.

[limeex2]

The post doesn't mention if it ran this way before pod and muffler removal.If it wont idle without choke, pilot circuits may be plugged or restricted. Before any jetting is attempted, make sure carbs are clean. Canned cleaners do not work.When I worked in the dealership, When we installed slip-ons We always bumped 1 up size on the pilot as all modern bikes are EPE'd certified and run lean in stock form to pass emissions and get worse with intake or exhaust mods. Just off idle, when in transition from idle circuits to needle, circuits can be fine tuned by shimming the needle up for more fuel. Yamaha dealers have a nice shim that are less than $1 each

[eran_k]

I'm rebuilding the bike so the carbs have been stripped, cleaned and all o-rings replaced (including the manifolds o-rings)
i never started it before tearing down but PO said it was running. it was totally stock.
carbs were pretty clean and nice inside even before i cleaned them.
I cleaned them according to the manuals on cliff's site and made sure all passages and jets are open and clean

[JTGS850GL]

How did you initially set the idle screw? It could be that the butterflies are too closed to allow it to idle. On mine the screw should be 2 to 3 full turns in after initial contact with the linkage pad. Not sure on the GSX400.

[eran_k]

Actually i think it's barely touching the butterflies, but aren't they supposed to be completely closed at idle?

[JTGS850GL]

Actually i think it's barely touching the butterflies, but aren't they supposed to be completely closed at idle?

No, they need to be open just a hair for the bike to idle. If they're completly closed then that will cause the problem you're having. Turn the idle screw in a couple of turns and see if that fixes the idle issue. Just be ready to hit the kill switch if the RPMs jump to high. If so, then back the screw out half a turn and try again.

[Steve]

No, they need to be open just a hair for the bike to idle. If they're completly closed then that will cause the problem you're having. Turn the idle screw in a couple of turns and see if that fixes the idle issue. Just be ready to hit the kill switch if the RPMs jump to high. If so, then back the screw out half a turn and try again.

See post #3.

.

[JTGS850GL]

There you go again Steve... Pointing out you were correct all along. Yep, sometimes people need to hear it twice before the light bulb turns on. Actually, they need to hear it worded in a differant way before it's fully understood. Hopefully a little adjustment on the idle speed screw will make all the differance.