Rough Idling

[Quick 350]

I'm not to familiar with the XS400 but the XS750 carbs had that Primary pump on the carbs and if the diaphragm has a leak or is cracked then those are some of the symptoms.

The only thing I see different is that in most cases the bike will only run with the choke on and wont start after it stalls out. Only after the bike cools down will it start again.

As for the Lucas question I was the one that suggested it. It worked out for me But remember it's an additive and one bottle = out for 4 Quarts of oil so break it down to the amount of oil used in your bike and only add that much.

Again my friend had a KZ 750 with over 60K miles and was in need of valve seals "Bad". when he took it to a local shop the guy gave a quote of $800+ with no guarantees unless he rebuilt the lower end as well $2,000+ the shop owner told him he would be lucky to make it home. Well over 4yrs two other riders and now 100K+ miles it's still going. "MIRACLE" maybe it won't hurt to try

[kar_the_terrible]

ugh!! diapraghm huh? Those are super expensive, and I think I might be broke very soon. Although I read somewhere that a condom and cyanoacrylate glue will help heal that... anyway thanks for the tip.. I'll look into it tomorrow.

[TechTMW]

GAAAA!!!

HELP!!! This is eating away at me and I cant sleep anymore

Take a step back from the Motorcycle... do something else for a while. Let the bike be.

I went to a friend's and dug up the specs on your bike... First of all, I'm showing a main jet of 132.5 and a pilot jet of 42.5 ??

Symptoms number two and five are indicative of a clogged idle circuit. Your idle circuit isn't flowing fuel, so the only fuel your bike is getting is from the enrichening circuit (choke). When you crack your throttle, you allow the needle jet/ jet needle to flow fuel, which allows the bike to run better.

Clean out the idle circuits. Take the carbs to get either a sonic or traditional dip. Check your diaphragms, and all other components upon disassembly, or let the shop do it.

[kar_the_terrible]

Im not sure about the jets. I pored over my haynes manual and chilton manual too, but they dont seem to be documented. I even inspected the jets for number printed on them, but they seem to be erased, almost unreadable. Are those jet diameters? if so what units??

Anyway, I noticed that the pilot jets were gunked up *again*... so Im cleaning them out. First I cooked the carbs in a dip. The diapraghms are fine. Now I think another cleaning with compressed air and carb cleaner is necessary. BTW... boiling them in vinegar and water realllly cleans stuff up. Not as much as a carb cleaner dip, but this got the float bowls and all the brass parts especially clean and shiny.

[TechTMW]

OK, you probably have stock jets, don't worry about it ... I actually got you confused w/ Shoey who mentioned his jet size in another post

So many small parallel twins running about these days !

Anyway - If your pilots were clogged w/ crud "again" as you put it, you might have alot of crud in your gas tank. And (This was the case on my bike) the plastic filter/tube inside the tank feeding the petcock may have popped out of its hole. I eventually fixed w/ some jbweld ... anyway, back to your case - if some crud is getting from your gas tank into your carbies, the first thing to clog will be your idle circuit. I recommend putting a fuel filter in between your petcock and your carb. (Might as well replace the fuel line too)


Don't start your bike until you do this and let us know how it turns out. Oh, and you'll probably need to synchronize the carbs again as well since you've had them apart again.

Don't worry, you'll get there !!

[kar_the_terrible]

I got it idling finally. Works great... thanks a lot!!! On to check other stuff .....