SteveP
XS650 Addict
And thanks for that Slowshed. I'm having to work through that info.
It takes me a while these days.
It takes me a while these days.
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Broken valve
- Thread starter SteveP
- Start date
and that might be it.
SteveP
XS650 Addict
I'll be on to that one tomorrow. The po managed to mess up the mains with a wrong screwdriver. I'll try to source some original ones the correct size.
Again thanks
Again thanks
SteveP
XS650 Addict
I've had a good look at my two sets of carburettors. It turns out that the height of the threaded boss that the float needle valve sits in is different. On the 1974 it measures around 5.3mm and on the 1976 it measures 5.8mm. measured with digital calipers.
I've attached photos that sort of show the different heights.
I'm tempted to put two washers under my needle valve housings.
It still doesn't help with my rich running
.
I've attached photos that sort of show the different heights.
I'm tempted to put two washers under my needle valve housings.
It still doesn't help with my rich running
.Attachments
A LOW float bowl fuel level won't make it run rich.
Have you confirmed ALL your brass matches the year of the carb body?
matched needles and needle jets a biggie.
Some are NLA.
Have you confirmed ALL your brass matches the year of the carb body?
matched needles and needle jets a biggie.
Some are NLA.
SteveP
XS650 Addict
I've checked all the brass bits. They are correct for the year. Though the mains are non mikuni.
I was thinking that the float heights wouldn't be the problem. I just wanted to get everything as original spec.
The rich running is on both carbs. Both plugs are equally sooty.
All that I can think that will effect both carbs is the single shared choke. Or the ignition system.
I've ordered a nos choke plunger.
The ignition components are all as original. Possibly fifty years old apart from the new Chinese points. There's a slight voltage drop of 0.3v between the battery and the coil. Advance mechanism cleaned and lubricated.
I think I will attempt to persuade her indoors that I need an electronic ignition system. If the choke plunger doesn't work.
I was thinking that the float heights wouldn't be the problem. I just wanted to get everything as original spec.
The rich running is on both carbs. Both plugs are equally sooty.
All that I can think that will effect both carbs is the single shared choke. Or the ignition system.
I've ordered a nos choke plunger.
The ignition components are all as original. Possibly fifty years old apart from the new Chinese points. There's a slight voltage drop of 0.3v between the battery and the coil. Advance mechanism cleaned and lubricated.
I think I will attempt to persuade her indoors that I need an electronic ignition system. If the choke plunger doesn't work.
Have you done the slide drop test? A choke that doesn't seal will affect the drop rate (they will quickly close).
Couldn't help but notice that your idle screw is almost fully wound in, the spring is almost coilbound. That looks like you would be idling around 2,000rpm (compared to 5Twins photo). Is that how yours is normally set? Just tryin' to figure this one out. 
Not read through so apologize if stupid
Air Filters dirty / wrong type ??
Perhaps a test ride without Air Filters
Air Filters dirty / wrong type ??
Perhaps a test ride without Air Filters
Maybe a dumb question but on an unlinked set doesn’t the choke only affect one carb?
SteveP
XS650 Addict
That's a good point. I did do a drop test. With the choke closed it took around 10 seconds for the pistons to drop, on both carbs. Opening the choke did make it drop faster. Sounds like the choke is working. Normally I'd be looking at slide cut-aways to adjust richness just above tickover. It doesn't seem to be an option for these carbs.
That's a good point about the idle screw being wound too far in. I thought I'd set the butterflies at exactly the same very small gap. Just gripping thin waxy paper. I'll definitely be checking that out. It's ticking over at 1200 rpm.
The filters are original frames recovered in filter foam. Lightly oiled. I'll be trying running without them to see if it makes a difference.
The choke is on the left hand carb but there is a connection tube to the right carb. I think that's how it it works.
Thanks again for all the help and ideas.
I'll be back out in the garage tomorrow morning.
That's a good point about the idle screw being wound too far in. I thought I'd set the butterflies at exactly the same very small gap. Just gripping thin waxy paper. I'll definitely be checking that out. It's ticking over at 1200 rpm.
The filters are original frames recovered in filter foam. Lightly oiled. I'll be trying running without them to see if it makes a difference.
The choke is on the left hand carb but there is a connection tube to the right carb. I think that's how it it works.
Thanks again for all the help and ideas.
I'll be back out in the garage tomorrow morning.
SteveP
XS650 Addict
I've got the shorter Z6 jets fitted. They were in the carbs originally. Are they correct?
I'm struggling to find suppliers for original mikuni jets here in the UK. Allens seem to be the main dealer. But they are out of pilot jets. Do you know what main jet type would be suitable
I'm struggling to find suppliers for original mikuni jets here in the UK. Allens seem to be the main dealer. But they are out of pilot jets. Do you know what main jet type would be suitable
I have also had issues getting original Mikuni and Keihin jets. I have had good results buying Keyster jets from NRP Carbs in Manchester. If they don't have what you need, I have had good results with Tourmax jets that I got from Motorcycle Products dot CO dot UK. Both Keyster and Tourmax are Japanese and I haven't bought anything of theirs that turned out to be bad. Good luck.
SteveP
XS650 Addict
Thanks for that. I'll have a look
SteveP
XS650 Addict
Sorry dumb question about Z6 jets. They are short as in the table above 
Thanks for that Gary. I didn’t remember that from the ‘75.
SteveP
XS650 Addict
I'm slowly working through all the information from everyone. Thanks again. The weather is not too good here so I'll be working in my unheated garage as and when.
I've found a similar post from a few years ago; https://www.xs650.com/threads/74-running-super-rich.50419/ loads of stuff to go through. It never concluded.
I've changed the fuel. Fitted new fuel filters. Packed the float needle valves 0.5mm higher. Set the floats at 24mm (again!!). Fitted a new choke plunger. New spark plugs. I'm ordering two Mikuni N102.221 main jets.
I'm waiting for the weather to warm up enough to soften the inlet manifolds so I can refit the carbs.
I was checking the compression with an old tester. I took out both new plugs and grounded them. Nice big fat spark on the right. Little spark on the left dancing around the electrode. I need to investigate.
I acquired a compression tester, dwell meter and Gunsons Colortune from a friend. Lots of things to try.
I will post any updates. And failures.
I've found a similar post from a few years ago; https://www.xs650.com/threads/74-running-super-rich.50419/ loads of stuff to go through. It never concluded.
I've changed the fuel. Fitted new fuel filters. Packed the float needle valves 0.5mm higher. Set the floats at 24mm (again!!). Fitted a new choke plunger. New spark plugs. I'm ordering two Mikuni N102.221 main jets.
I'm waiting for the weather to warm up enough to soften the inlet manifolds so I can refit the carbs.
I was checking the compression with an old tester. I took out both new plugs and grounded them. Nice big fat spark on the right. Little spark on the left dancing around the electrode. I need to investigate.
I acquired a compression tester, dwell meter and Gunsons Colortune from a friend. Lots of things to try.
I will post any updates. And failures.
A hair dryer or heat gun works well to soften the intake boots. It will work for cold temperatures but also for old, hardened rubber boots.
One more thought on the rich condition … did you remove the air jets when you rebuilt the carb? I have seen the air jets mixed up and cause a very rich condition. A buddy of mine did that on an XV750 years ago. Took him some time to figure that out.
One more thought on the rich condition … did you remove the air jets when you rebuilt the carb? I have seen the air jets mixed up and cause a very rich condition. A buddy of mine did that on an XV750 years ago. Took him some time to figure that out.
condenser?
When I'm overhauling carbs I typically take a fine file and SLIGHTLy round the edge of the carb spigots engine and air filter side. there's often a bit of flash from the molds there.
A bit of lube eases penetration,
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