Firing her up after my first carb rebuilt *Pics & Vid*

[Titans]

Hey all!!

Last week I was successful in putting the carbs back together which allowed me to mount them and replace all the fuel lines (they were hardened and brittle).

So she runs (I put on about 100km today ), but she can definitely run better. Idle is still a little rough and choke will kill the engine (both choke settings). I can't start her on choke and when I do get her going (sans choke) then switch it to choke: the RPM's will momentarily rise (~+1000RPM) then drop to dead. Any ideas? Mixture screws too rich? When cleaning I didn't pull the choke slide yet I am pretty sure I had carb cleaner flowing through the channels there. Please ask away

I made a little video for you guys:
<iframe width="420" height="315" src="http://www.youtube.com/embed/O9K_JO8rB-E" frameborder="0" allowfullscreen></iframe>
I believe the audio in the video makes the bike sound a little rougher than she is in reality; mmm.. perhaps I'm just biased though .

Mixture screws are two turns from seated and the carbs have not been synced. This leads me to another question: which should come first, mixture screw adjusting or carb sync?

Some pics:

[BA80]

Your video link didn't work.

The sync and mixture adjustment needs to be done at the same time as one will affect the other.

[Titans]

Your video link didn't work.

The sync and mixture adjustment needs to be done at the same time as one will affect the other.

http://www.youtube.com/watch?feature...=O9K_JO8rB-E#!
I can't seem to edit my initial post!? Also, can we not embed video's on this forum?

Got it, colour tune and sync then check the colours again! (Now I need to get access to a colourtune!?)

[BA80]

I used to know how to do the videos but I've forgotten now.

It sounds good but your idling a bit low. It works best idling between 1000 and 1200 fully warmed up. But, for the sync it needs to be 1000 or less.

You can color tune but it's really unnecessary in my opinion. The idle mixture can be adjusted with the sync guages and is really the only proper way to do it.

Sync the carbs then adjust the mixture screws to the highest vacuum reading IDIVIDUALLY then resync.

Repeat the above until the readings remain the same. You'll probably need to set the idle down a time or two because as you get things adjusted it will increase

It may take several rounds of this to get it right. A large fan blowing over the engine may be needed to keep it from overheating.

Best method I have found.

[petejw]

just regarding the choke,
when u had the carbs apart did u clean the small jet
in the fuel bowls?
also ur float settings can effect the choke did u set
them to stock specs?
gregs got u covered for the rest of it.

[DGXSER]

From the sound of it, you definitely need to synch them up. And tune. And I always synch first, then tune, then resynch. But it really does not matter which one comes first, as long as you do both.

[Titans]

Sync the carbs then adjust the mixture screws to the highest vacuum reading IDIVIDUALLY then resync.

Repeat the above until the readings remain the same. You'll probably need to set the idle down a time or two because as you get things adjusted it will increase

Are you saying then that the optimal mixture setting will yield the highest vacuum reading? The corollary is that any leaner or any richer will retard the vacuum?
If so, that's a great way to do it! (I'm acquiring the gear to make my own Bernoulli principal vacuum readers. i.e. liquid in tube)

just regarding the choke,
when u had the carbs apart did u clean the small jet
in the fuel bowls?
also ur float settings can effect the choke did u set
them to stock specs?
gregs got u covered for the rest of it.

Definitely got the little jet in the float bowl area. I then used my verniers to equalize the floats 27.x mm (Claymers) from the gasket area; however, I think I read today that the claymers was wrong for the 81 SH's?

From the sound of it, you definitely need to synch them up. And tune. And I always synch first, then tune, then resynch. But it really does not matter which one comes first, as long as you do both.

Suppose that will solve my choke issue?

[BA80]

From the sound of it, you definitely need to synch them up. And tune. And I always synch first, then tune, then resynch. But it really does not matter which one comes first, as long as you do both.

I think a sync should be done before messing with the mixture screws just to prevent any false readings with the mixture.

But, that's just me.

[ddragon63]

I used to know how to do the videos but I've forgotten now.

It sounds good but your idling a bit low. It works best idling between 1000 and 1200 fully warmed up. But, for the sync it needs to be 1000 or less.

You can color tune but it's really unnecessary in my opinion. The idle mixture can be adjusted with the sync guages and is really the only proper way to do it.

Sync the carbs then adjust the mixture screws to the highest vacuum reading IDIVIDUALLY then resync.

Repeat the above until the readings remain the same. You'll probably need to set the idle down a time or two because as you get things adjusted it will increase

It may take several rounds of this to get it right. A large fan blowing over the engine may be needed to keep it from overheating.

Best method I have found.

+1 I followed this method when I did mine... Takes a little time going back and forth but worth it in the end.

[natemoen]

I then used my verniers to equalize the floats 27.x mm (Claymers) from the gasket area; however, I think I read today that the claymers was wrong for the 81 SH's?

If you have the original carbs you need to be at 23 +/- 1mm. 27 would be WAY lean.

[Titans]

If you have the original carbs you need to be at 23 +/- 1mm. 27 would be WAY lean.

To be honest, I'm not sure on the top of my head what it's set at, but I followed the Claymer's manual to a tee. Perhaps it's 23.7mm? (the 7 rings a bell)

[crazy steve]

To be honest, I'm not sure on the top of my head what it's set at, but I followed the Claymer's manual to a tee. Perhaps it's 23.7mm? (the 7 rings a bell)

The early carbs with the brass floats are set at 25.7 mm. The late carbs with plastic floats (or early carbs that have been converted to plastic floats) are set at 23 mm. Getting this wrong will be a big problem...

[Titans]

The early carbs with the brass floats are set at 25.7 mm. The late carbs with plastic floats (or early carbs that have been converted to plastic floats) are set at 23 mm. Getting this wrong will be a big problem...

Thanks Steve! I'll pull the carbs and verify the position because come to think of it, I think it's set to 25.7mm!

[mjpxs11sh]

+

hey Titan. i just went thru this with my SH (they could kinda be twins but mines a mutt) and i set the plastic floats at 23mm and also checked the fuel level at the bowls an external fuel tube connected to the drain on each carb (as in the OEM manual) then set my mixtures at 2.5 turns out from light seat. i found 2.5 turns the best after several road tests and some manual fine tuning. i havent sych'd or set mixture yet but will when i buy some guages. my bike runs great and starts with 1 crank, so its gotta be close. good luck and thats a nice bike! i know the feeling of accomplishment when it runs decent after doing successful work.