Inlets (Pics) Part 2, Bench Sync and Vacuuming

[Guest]

Hi all, Many thanks to one and all for their contributions to my previous threads, and for the handy tips hints and advice on removing stubborn inlet screws.

I have them removed now.. and here they are.. 'O' Rings as flat as could be, but no obvious signs of leaks.







I have ordered replacements, and new 'O' Rings so that should sort out the cylinder side..

Airbox side: I pulled these out..







These have had it too I'm guessing and will cause carb/vacuum problems ?

So: Can anyone enlighten me on 2 more issues.

Bench synching.. I have adjusted both throttle butterfiles so they open at identical times, using a small wire as a guide. I have replaced all inner 'O' rings, set both air screws to 2.5 turns (as a starting point) . What else do I need to do ?

I also see that Vacuum synching is important, but despite searching I can't find out what this involves,(I've never done this) Is the Morgan Carbtune the best tooling to purchase. And lastly, can anyone explain what's involved in doing this and how do you adjust the carbs vacuum.

In other words how does a vacuum synch tool work and how do you alter settings..

Thanks Guys.. You have been briliant help so far, much appreciated

[loud et]

This is decision time!
To really be sure, and have a good running bike.....you really need 4 new intake boots(yours are cracking away at the metal base and are prone to leaks), new intake o rings for the boots and new air box boots.
It will be the best 200$ you spend in your bike.
Using a sync tool would be a waste at this point until you replace the above mentioned items.
None of us want to spend the money when we are new to these bikes but after time spent struggling with a poor running bike we get over the money thing and buy new boots.
Ad far as the carb rebuild goes, don't forget to set the float height.
Other than that your bench sync sounds good and your bike will start and probably run ok.....AFTER you replace all that worn out rubber intake stuff.

[tom203]

The vacuum sync is just a more refined adjustment on the bench sync. Have a look here.....

http://www.bwringer.com/gs/carbsync.html

[grana]

Carb balance

Hi
This might help ,im also looking into this ( carb balance on gsx uk
gs usa 16 valve 750 1980)

http://www.bwringer.com/gs/carbsync.html

CHEERS

[Steve]

...you really need 4 new intake boots(yours are cracking away at the metal base and are prone to leaks), ...

Methinks you are doing some assuming here.

He only showed THREE intake boots. Was that "three out of four" or "two views of one, and a single view of the other"?

Here is why I am wondering:

Bench synching.. I have adjusted both throttle butterfiles so they open at identical times, using a small wire as a guide. I have replaced all inner 'O' rings, set both air screws to 2.5 turns (as a starting point) . What else do I need to do ?

Sounds more like he has a TWIN, not a FOUR.


Showtime, what you need to do is to tell us what bike you are working on. Either mention it in every post where you are asking questions about it or just put in in a signature, which will do the "mention it in every post" for you.

Besides knowing the size of the bike, we need to know the year, because "air screws" don't exist on the twins or any of the fours from '80 and up. If you indeed adjusted some "air screws", you have VM carbs and 2.5 turns is only a good starting point if your fuel screws are at about 1.25 turns, which is way too much. If you have BS carbs (also known as "CV" carbs), 3 turns is a better starting point, even though they might end up close to 2.5.

.

[wymple]

My airbox side rubbers were shot, and a road trip looming too soon to get new ones, I improvised. I had quite a few pod filters laying around from past chopper and project stuff. I found 4 that had the necessary 52 mm mouths to fit the carbs on my GS850. You can buy 4 brand new ones on ebay for around 20 bucks shipped. I pulled the rubbers off of them and clamped them onto the carb bank. The 2 inch holes in the airbox just fit over the pod ends. It's not quite the perfect seal, but is very close. So I ran some RTV black around the pod rubbers and let it set up for about an hour, the pushed the airbox into place. I have a perfect seal on all 4 and the pods have a better mouth to sit on the carbs than the original rubbers ever did. They are slightly deeper and ribbed as well. I highly doubt I will bother to buy new factory type stuff now. The originals had a small extension that juts back into the airbox, but the bike runs like a champ, so I guess that doesn't mean much.

[Showtime]

This is decision time!
To really be sure, and have a good running bike.....you really need 4 new intake boots(yours are cracking away at the metal base and are prone to leaks), new intake o rings for the boots and new air box boots.
It will be the best 200$ you spend in your bike.
Using a sync tool would be a waste at this point until you replace the above mentioned items.
None of us want to spend the money when we are new to these bikes but after time spent struggling with a poor running bike we get over the money thing and buy new boots.
Ad far as the carb rebuild goes, don't forget to set the float height.
Other than that your bench sync sounds good and your bike will start and probably run ok.....AFTER you replace all that worn out rubber intake stuff.

Thanks All for the input, Ahem.. My error again.. Bike is indeed a Twin (GS450 S) So sorry to distract you all with unnecessary guesswork that went off topic.

Loud.. Agreed.. I have already ordered the inlets and 'O' Rings , should be here this week, It was only when I pulled the Airbox rubbers that I could see how bad they were.. so they too will be replaced..

I'll happily spend the money getting it to run right before I tear it down and do a resto on it.. waste of time if the motor is shot..

But so far , all the input and work so far has improved bit by bit the running, so proof that you are all right on air leaks and sealing is absolutely critical to these bikes.. lessons being learned.

I've never worked on a vacuum operated carb setup before, been an experience !!

Once all boots have been replaced, inlets changed and 'O' Rings installed will be back for a Vacuum update

Thanks again

[Showtime]

Methinks you are doing some assuming here.

He only showed THREE intake boots. Was that "three out of four" or "two views of one, and a single view of the other"?

Here is why I am wondering:


Sounds more like he has a TWIN, not a FOUR.


Showtime, what you need to do is to tell us what bike you are working on. Either mention it in every post where you are asking questions about it or just put in in a signature, which will do the "mention it in every post" for you.

Besides knowing the size of the bike, we need to know the year, because "air screws" don't exist on the twins or any of the fours from '80 and up. If you indeed adjusted some "air screws", you have VM carbs and 2.5 turns is only a good starting point if your fuel screws are at about 1.25 turns, which is way too much. If you have BS carbs (also known as "CV" carbs), 3 turns is a better starting point, even though they might end up close to 2.5.

.

Steve.. Yes you were right, indeed it is a twin.. 1980 GS450S.. pics were of each inlet L & R and then another shot from different angle.. Airbox boots were also both boots then taken from above together. both shot..