Carb rebuild on 78 std

[Chuckster]

First time posting here, have been lurking for the last few weeks as I attempt to resurrect my 78 std from the dead. I have let it sit for a bunch of years (I know I'm stupid) but have committed to getting it going again. First I want to say thanks because I never would have attempted this without seeing the info and knowledge here on this site.

I have pulled the carbs off and using rebuild kits have replaced the float needle/seat, main jets and pilot jets, along with cleaning everything. Since the bike always ran great (granted a long time ago) I did not do anything with the idle mix screw, needle or float height. My plan was to leave those alone, put the carbs back on and see how it runs. Then do a carb synch.

Am I unwise to leave these as is? Now that I have everything off and apart is it smarter to replace/adjust these as well?

Any advice would be appreciated.

[randy]

Chuckster, if you didn't do anything with the idle mix screw, how did you "clean everything out"?

That pilot jet passage leads all the way from the bowl up to the mix screw, remove the screws to clean out the whole passage.

Set the idle mix screws to 1-1/4 turns out from lightly seated for a start. Then during the synch you can adjust them one by one for the highest smoothest idle.

Check your float heights with a micrometer NOW, before you close things up.

[Chuckster]

Thanks! Obviously I'm new to this and I didn't realize that. The manual had me paranoid about changing things, I will definitely do as you suggest.

[jwoell]

Just a thought, but what carb rebuild kits are you using? There has been a fair amount of discussion about the jets in K&L kits being incorrect for some bikes. I'm not sure which years and all that, but I know I got bit in the arse by this one and it took me way way too long to figure it out. Anyway, just thought I'd mention it just in case you happen to be using the K&L kits. Save your original jets.

Definitely take out the pilot screws and clean everything. Also you may want to replace the little o-rings and stuff in there, so it's important not to skip that. Not to mention that you really need to adjust them as part of the sync'ing process anyway.

I would also check all the float heights and make sure they're at least the same on each carb. Preferably set them all to the level the manual calls out (which I don't remember right now on the early bikes, but I'm sure someone will mention it I though it was 27.5mm but I could be off on that)

Oh and be sure to take out the emulsion tubes and clean them and the area they mount in too. They should come right out the top of the carbs once the main jets are removed.

Hopefully I didn't get things all mixed up, I have an 81 and I know there are a few differences in the early and the later carbs, so take this post with a grain of salt

[Chuckster]

You are correct, the kits are K&L. The main jet is 137.5 and the pilot is 45. Sounds like this could be a problem...

[red bandit]

You are correct, the kits are K&L. The main jet is 137.5 and the pilot is 45. Sounds like this could be a problem...

Shouldn't be a problem. Save your old jets anyway, just in case. If you don't need em you could probably sell them to someone on here... maybe me.

[skids]

If it is K&L pilot jet set and has eight holes in the shank of each jet, it wil be way to rich. Yeah, save your old ones. They can be cleaned.

Originally posted by red bandit


Shouldn't be a problem. Save your old jets anyway, just in case. If you don't need em you could probably sell them to someone on here... maybe me.

[SanDiegoMike]

It ran fine before...

...famous last words. Very smart of you to go through them and get them set up correctly. You can go back to original settings AFTER everything is removed (including needle jets/emulsion tubes...DAHIK) and dial it in from there. Glad to hear you're motivated to get back on the road! Welcome to the site!!