Idle and Throttle Sync Test

[Pio412]

Just to help my sanity i want to know what everyone thinks of my sync here. is it good enough? For some reason i still seem to have a tiny bit of surging while riding with steady throttle... does it still need adjusted? is there anything else that might cause surging with a good throttle sync?

sorry for the vertical video....

idle - https://www.youtube.com/shorts/h3mI-fPY0o0

throttle - https://www.youtube.com/shorts/WBFg6QjTsSM

[navigator]

That looks close enough to me.

[Designer]

Wellsir,....If'n it twere me,......I'da kinda-sorta put just a wee bit of a tweek on the Idle settings,.... so's dat dey match pre-zactly.

About your "Throttle" setting (at 2000 RPM) ,....since that is near-where the Engine is most all the time when Riding, I like to make it just as exacting.

What I do to achieve this is to use the Throttle Cable Adjusting Barrel at the Grip to raise the Engine speed and hold it steady. That way I can take my time to fine-tune that Balance setting for Max Smoothness on my Bad Boy Choppah.

[Pio412]

Wellsir,....If'n it twere me,......I'da kinda-sorta put just a wee bit of a tweek on the Idle settings,.... so's dat dey match pre-zactly.

About your "Throttle" setting (at 2000 RPM) ,....since that is near-where the Engine is most all the time when Riding, I like to make it just as exacting.

What I do to achieve this is to use the Throttle Cable Adjusting Barrel at the Grip to raise the Engine speed and hold it steady. That way I can take my time to fine-tune that Balance setting for Max Smoothness on my Bad Boy Choppah.

Ahh you're right designer, the idle just needs a slight tweak. I guess I'll have to get to building your design you posted for the carb adjustment mod with the tank on because I'm dreading tweaking these buggers again!

[navigator]

I'd be willing to bet you could wiggle the idle sync cable and make it spot on.
Vibration and bumps in the road will do that. JMO

[Pio412]

It's kind of weird though, sometimes when I give it steady throttle when at a stop, the rpm's tend to drop a bit.

[navigator]

You could adjust your A/F mixture for best idle.

[Pio412]

Thing idles perfectly, rpms just drop a bit when throttle held at 1500-2000 rpm

[sgtcall]

It's kind of weird though, sometimes when I give it steady throttle when at a stop, the rpm's tend to drop a bit.

Sounds like you don't have star washers on your battery terminals.

[Herb]

Thing idles perfectly, rpms just drop a bit when throttle held at 1500-2000 rom

Sounds like it is a little lean on the top end. Maybe the needles are a little off.

[Pio412]

Thing idles perfectly, rpms just drop a bit when throttle held at 1500-2000 rom

Sounds like it is a little lean on the top end. Maybe the needles are a little off.

You would think that but this thing is completely stock. (minus removing fuel mixture screw tamper plugs) I have noticed though that when i give it half choke she rides as smooth as butter..... could the pilot circuit really be clogged up? When i got this thing in 2022, I completely rebuilt the carbs, new gaskets, float needles, set the float levels, new fuel mixture screw gaskets, set the idle mixture screws. Blew through all the ports and passages etc. Made sure all cables and fuel lines were routed properly etc.... Synced her up as close as i could get (as shown on the videos) At a stop this thing revs smooth and idles perfect. But when under load with no choke it sputters. These test rides where in 48 - 50 degree Fahrenheit weather. Does this thing really need 10+ minutes to warm up with choke?

what to do next...

[Designer]

Your symptoms I have heard before. Tell me,...what Pipes do you have on your 1400?

[sgtcall]

Your symptoms I have head before. Tell me,...what Pipes do you have on your 1400?

I think it is a VS800 unless he changed bikes. The pipes look stock to me.

[YoutubeURL][/YoutubeURL]

[Herb]

Long time ago my 87 1400 was doing about that kind of thing. Even running a steady speed on the highway it would loose RPM's. I finally found out that there were a bunch of holes in the diaphram that works the slide.

The only thing was that it ran great at idle.

[Designer]

Your symptoms I have head before. Tell me,...what Pipes do you have on your 1400?

I think it is a VS800 unless he changed bikes. The pipes look stock to me.

Hmmm....I didn't see that perspective in the two video clips at the top of this page. And yes,...In that one it is a 800.

It does look like Stock Pipes.

[Pio412]

Your symptoms I have head before. Tell me,...what Pipes do you have on your 1400?

stock.

and its an 800, sir

[Pio412]

Long time ago my 87 1400 was doing about that kind of thing. Even running a steady speed on the highway it would loose RPM's. I finally found out that there were a bunch of holes in the diaphram that works the slide.

The only thing was that it ran great at idle.

hey Herb,
i can see that being an issue, but i thoroughly inspected both diaphragms when i rebuilt the carbs. They looked new.

Another side note i did run 89 octane in it after the rebuild... could that cause this issue? Shouldnt it be 87?

[Designer]

Your symptoms I have head before. Tell me,...what Pipes do you have on your 1400?

stock. and its an 800, sir

Yes, I see that now that SgtCall posted a video from another Thread.
I think I see your point. An Octane rating of 87 usually burns a bit quicker that a higher rating. However, given what you post as symptoms, I sincerely doubt the RPM drop you are experiencing is due to Octane rating.

Just to ask,....have you checked the Exhaust Pipe-to-Head Flange Bolts?

[sgtcall]

Just to ask,....have you checked the Exhaust Pipe-to-Head Flange Bolts?

Good point. Have you put on new crush gaskets? I found that you could reuse the old ones a couple of times but after that you need to replace them. I have no idea if that is the issue but it is good to do.

[Designer]

Just to ask,....have you checked the Exhaust Pipe-to-Head Flange Bolts?

Good point. Have you put on new crush gaskets? I found that you could reuse the old ones a couple of times but after that you need to replace them. I have no idea if that is the issue but it is good to do.

Spot On, SgtCall.
An exhaust leak at this point in the System can be the cause of several performance issues. Depending on how big the leak and if it's one or both cylinders, it can cause RPM changes at Cruise Engine RPM ( little load) or while Accelerating, Misfiring/ Power Loss/etc. ( under more load). At Idle it may not even be detectable! (again, depending on how big the leak and if both cylinders).

I recall several times on the Purple Board, guys going nuts trying to fix mysterious symptoms,... Repeated Adjusting/Tearing into the Carbs and Fuel System/Pump, etc.......... spending loads of time on the Ignition/Electrical System checks,......only to find it was Loose/Leaking Header Pipe Gaskets.

Being SO easy to check,...It's now my FIRST item on my trouble-shooting list for these symptoms such as pio142 reports.