How lean to go

[Paul Kelly]

Just bought a nice 81 GS1000GL which has just had a big bore kit (1083) installed (by previous owner). He did nothing with the carbs as far as re-jetting.

The bike has a Mac header (4 into 1) and a stock filter does anyone know or care to suggest what size of jet I should use and whether the needle needs to be lowered and if so by how much?

I have just installed 107.5s bike runs...ok sort of at constant speed..but bogs under acceleration.

[tkent02]

Wouldn't think you would need to change much, how did it do with the stock jets?

Do some plug chop tests, then you will know.

[Zooks]

Keith Krause is the guru on such things (amongst others). Hopefully he will see this (if you are patient). If not, you could send him a PM. He's a nice fella, I'm sure he wouldn't mind. Good Luck.

[chef1366]

Let's see. Stock for your Canadian model should be.
115 main jets
42.5 pilot jet
160 pilot air jet
jet needle at middle notch.
With a 4-1 pipe (I hear Mac doesn't breath much more than stock) and a big bore. How big?
Wth a stock airbox I would start with a 122.5 main and raise the needle one notch. (but the e-clip on the needle down one notch) You might have to bring out the idle mixture screws a half to full turn out.

[Paul Kelly]

repy to my query how lean to go

Thanks for the input. The big bore kit is 1083 and the bike runs way too rich on the stock jets. I've downsized to 107.5s and am almost there mix wise but still a little rich..
My next step was to install an after market filter similar to K&N but would appreciate advice on of needle position which is still in stock configuration.

Bike bogs when the throttle is opened up from 3-4000 but seems to run ok under constant throttle at any speed. Plugs are black but not as fouled as they were with the 115 jets

[Nessism]

Thanks for the input. The big bore kit is 1083 and the bike runs way too rich on the stock jets. I've downsized to 107.5s and am almost there mix wise but still a little rich..
My next step was to install an after market filter similar to K&N but would appreciate advice on of needle position which is still in stock configuration.

Bike bogs when the throttle is opened up from 3-4000 but seems to run ok under constant throttle at any speed. Plugs are black but not as fouled as they were with the 115 jets

The pipe will lean the mixture, not cause it to run rich. Sounds like you have leaky needles or petcock causing a rich condition. Either that or your jets are worn to the point of opening up the orifices. One other thought is a weak ignition causing the bike to seem rich due to incomplete combustion.

Good luck.

[chef1366]

There is no way you are rich with 107.5s. There is something up with weak spark or something.

[Paul Kelly]

how lean to go

Thanks for the input. Any ideas what would cause weak spark across all cylinders? That is if spark is the cause of my probs

[49er]

Thanks for the input. Any ideas what would cause weak spark across all cylinders? That is if spark is the cause of my probs

Before you check the spark, are you sure that the float levels are correct?

The fact that the motor responds well up top could mean that your float bowls are flooding. The effect of this is most obvious in the lower to mid rpm range. The fact that you are able to run leaner than stock mains also points in this direction, or a badly clogged filter!
Weak spark often shows up with missing at higher rpms.

[Paul Kelly]

New filter will be installed today so I'm trying that before going on to anything else. I figure small steps is best and helps me get to know the bike. Thanks for the help guys.

[Paul Kelly]

[quote=Paul Kelly;795311]Stays wheres yer at till I gets where yer to

[Paul Kelly]

A quick visit to my local Suzuki dealer brought to light the fact that the original spec plugs for my GS1000GL which were B8ES are no longer available and that we are now using BR8ES plugs which have a resistor in them.

Does anyone know if these new plugs actually have the same spark as the original spec ones or is it weaker when matched up to original coils. Is there a better replacement from NGK or another manufacturer?

One of you helpful fellas pointed out that my problem under acceleration (breaking up) and the remaining slight richness of the fuel air mix could actually be a weak spark condition. I'm trying to cover all the bases before the real season starts.

[Nessism]

A quick visit to my local Suzuki dealer brought to light the fact that the original spec plugs for my GS1000GL which were B8ES are no longer available and that we are now using BR8ES plugs which have a resistor in them.

Find a new dealer, seriously. B8ES plugs ARE available, and any self respecting dealer will have them in stock. Go find the dealership owner and tell him that his parts department is spewing out BS and you don't appreciate it.

Regarding the issue at hand, you might want to check out the voltage at your coils and your spark plug caps (they often break down with age). Z1 enterprises sells NGK plugs and plug caps for reasonable prices.

Good luck.

[Steve]

Find a new dealer, seriously. B8ES plugs ARE available, and any self respecting dealer will have them in stock.

... and if your dealer does not have them, go to the auto parts store.
The Auto Zone near me does not carry NGK plugs, but the Pep Boys just down the road does. \\/

.

[seuadr]

both murrays and advanced auto carry'em too.