Starting the bike and Idle Issue

[Surfrat28]

Hey everyone hope you guys had a nice Memorial Day weekend!

Bike: I have an 79 xs650 bored out to the 707cc with a Boyer ignition system installed to give me the bare minimal wiring for a chopper style bike with a kick only setup.

Issue:
I do have spark. The only way I can get the bike to start or fire is to place a glove around each carb to create a vacuum to get gas to the engine. I can get the bike to turn over but not idle or run for more than a few seconds. I have gone through each carb and it is near spotless.

Question: Is there any other way that gas would not be going to the engine? I will go through and check once again to see if the pilot jet I clogged.

Any help would be much appreciated!!

 

[figure8]

Are you using stock or aftermarket carbs? What exhaust and what air filters are you using? I went through something similar once when my float height was set incorrectly.

 

[Surfrat28]

Stock Carbs with K&N air pod filters and 12" Shorty Mufflers. This bike was bored out to the 707 kit.

Are you using stock or aftermarket carbs? What exhaust and what air filters are you using? I went through something similar once when my float height was set incorrectly.

 

[figure8]

Stock Carbs with K&N air pod filters and 12" Shorty Mufflers. This bike was bored out to the 707 kit.

View attachment 100483 View attachment 100484

Did you reject the carbs to accommodate the mufflers and pods? You'll need to go up 1-2 to sizes on pilots and 1-3 on mains with that setup.

 

[Surfrat28]

Did you reject the carbs to accommodate the mufflers and pods? You'll need to go up 1-2 to sizes on pilots and 1-3 on mains with that setup.

My main is at 135.5 and I am not sure what my piolet jet. I will see what I can order from a local shop

 

[figure8]

Here's the carb guide, there's a chart with stock jet sizes for different year carbs. Assuming yours are the matching 79's that came with your engine, looks like you still have stock jetting which would be to lean.
http://www.amckayltd.com/carbguide.pdf

 

[Surfrat28]

Here's the carb guide, there's a chart with stock jet sizes for different year carbs. Assuming yours are the matching 79's that came with your engine, looks like you still have stock jetting which would be to lean.
http://www.amckayltd.com/carbguide.pdf

Thank you I will read through this and see what I need to do. It sounds like I need to go up a few sizes in order to get this thing to run.

 

[figure8]

Thank you I will read through this and see what I need to do. It sounds like I need to go up a few sizes in order to get this thing to run.

No problem, best of luck.

 

[xjwmx]

Thank you I will read through this and see what I need to do. It sounds like I need to go up a few sizes in order to get this thing to run.

Pay attention to the part about the choke, because it sounds to me like your choke might not be working. Might also be super lean because of the floats or float height.

 

[Surfrat28]

No problem, best of luck.

I got the bike to fire after some cleaning but it still wont fire without me adding some pressure to the carbs and this is what I get. I was going to try and run straight pipes but I think it might be an issue with the stock carbs and jetting. I know people like Dan_motornation and Huge from Huges hand built run them constantly any thoughts if that could be my issue??

https://www.facebook.com/video.php?v=10208897188563057

 

[figure8]

I got the bike to fire after some cleaning but it still wont fire without me adding some pressure to the carbs and this is what I get. I was going to try and run straight pipes but I think it might be an issue with the stock carbs and jetting. I know people like Dan_motornation and Huge from Huges hand built run them constantly any thoughts if that could be my issue??

https://www.facebook.com/video.php?v=10208897188563057

Your video link isn't working. You said you cleaned, did you rejet? Did you check float levels while you had the carbs apart?

 

[peanut]

Could you try and upload your video to youtube ? so we can hear the problem.
Sounds like a fuel starvation problem.
When the engine next cuts out , turn off the petcocks and try undoing the brass drain nut on the fuel bowls and check you still have some gas in the bowls . No gas then its possibly a problem with the petcocks or the float height settings, or an air lock, or inline fuel filters the wrong way round , or petcock filters blocked with fine rust sediment.

Try disconnecting the fuel pipe from the petcocks and running some fuel into a jar to check you have sufficient fuel flow

If your carbs are stock 79 BS38s then as surfrat says you'll need to go up from stock 27.5 to 30 on the Pilots in order to be able to adjust the idle mixture screws sufficiently .
I've currently fitted 32.5 pilot jets for testing on mine which has straight thru mufflers and foam filters.
Make sure that you order the correct pilot jets. There are 2x types . This is the pattern you need for 79 BS38