Carb cable mods.

[toglhot]

Nobody does anything properly these days. I bought some VMs a month or so ago and found the cable ends that sit in the adjusters on top of the carbs are a very sloppy fit inside the brass adjusters, so today I pulled them out and took some measurements. The hole in the brass adjuster where the cable end sits is 7mm, whereas the cable end is only 6mm doesn't sound like much but that 1mm allows the cable end to flop around inside the adjuster. I spun up a couple of brass sleeves that were 6mm inside and 7.05 on the outside then pressed the sleeves into the adjusters, I couldn't risk making the fit any tighter as the walls of the sleeve were only .5mm thick. All worked out well, now the cables are a good fit, as they should have been from the shop. Why doesn't anybody supply good fitting accessories anymore?

Whilst I was at it I made a Spanner to fit the carb caps so I could tighten them reasonably tight. The spanner is aluminium so as not to scratch the polished caps too much. Previously, when I made the throttle cable, I made the inner cable a bit too long , so the adjuster in the throttle was at the end of it's adjustment, that also had to be fixed by removing the ******, cutting 8mm off the cable and refitting the ******.

After putting everything back together I started the bike and synced the carbs at idle, then increased the revs to around 3k and synced again, all good, or so I thought. Then I found as the revs rise upwards of 4-5k the left inlet tract on the left pot loses vacuum putting the carbs out of sync at higher revs. So, I synced the carbs at 4-5k revs then took it back to 3k revs and damn it, the sync is out again. Sync at idle remained constant and even More mucking about to find the problem.

 

[Busted Knucles]

A bit confusing, Are you syncing the carbs by adjusting the cables? That's not right.

 

[toglhot]

Ok, this should be good, how do you do it?

 

[toglhot]

Come on busted knuckles, entertain me! BTW you spell knuckles with a k after the c. No need to thank me, but come on, tell me how you sync carbs without adjusting the cables, I'm very interested.

 

[Old Man Roger]

If I had to guess, carbs that have secondary butterflies are synchronized differently than carbs with just slides? I've only sync'd carbs on an inline 4 through the butterfly. I've never sync'd dual carbs with just slide's, maybe knucles hasn't either?

 

[toglhot]

Not at all, the 74 TX 650 and a few others don't have linked carbs, they have a separate cable for each carb coming from a twin cable throttle, so they are synced the same way, by adjusting the cables. The pictures show the carbs aren't standard BSs and obviously slide only carbs, He obviously didn't put his brain in gear before engaging his mouth, guess he's also blind. I'm still waiting for him to entertain me though. Come on man who can't spell his own nickname, entertain me???

 

[Old Man Roger]

My first real street bike was an xs 650, an 82 or an 83 if I remember correctly. Pretty much the same as your 74. I do remember it was a Heritage Special, black and chrome. I did nothing but abuse that bike and it just ran and ran lol

Had a few enduros before that, but they were mostly used in the dirt.

 

[Jackfre]

Having been tormented by a set of Weber DCOE’s I was looking to follow this thread as I thought it would be interesting. Given its turn, I guess not. Good luck with your carbs

 

[Walkers]

Having been tormented by a set of Weber DCOE’s I was looking to follow this thread as I thought it would be interesting. Given its turn, I guess not. Good luck with your carbs

Weber DCOEs are the easiest thing in the world to sync. I have two up on a shelf, and hey are both holding down equal sized stacks of paper. If they are not synced simply move paper from the taller stack to the shorter stack.

 

[FredWanaker]

Nobody does anything properly these days. I bought some VMs a month or so ago and found the cable ends that sit in the adjusters on top of the carbs are a very sloppy fit inside the brass adjusters, so today I pulled them out and took some measurements. The hole in the brass adjuster where the cable end sits is 7mm, whereas the cable end is only 6mm doesn't sound like much but that 1mm allows the cable end to flop around inside the adjuster. I spun up a couple of brass sleeves that were 6mm inside and 7.05 on the outside then pressed the sleeves into the adjusters, I couldn't risk making the fit any tighter as the walls of the sleeve were only .5mm thick. All worked out well, now the cables are a good fit, as they should have been from the shop. Why doesn't anybody supply good fitting accessories anymore?

Whilst I was at it I made a Spanner to fit the carb caps so I could tighten them reasonably tight. The spanner is aluminium so as not to scratch the polished caps too much. Previously, when I made the throttle cable, I made the inner cable a bit too long , so the adjuster in the throttle was at the end of it's adjustment, that also had to be fixed by removing the ******, cutting 8mm off the cable and refitting the ******.

After putting everything back together I started the bike and synced the carbs at idle, then increased the revs to around 3k and synced again, all good, or so I thought. Then I found as the revs rise upwards of 4-5k the left inlet tract on the left pot loses vacuum putting the carbs out of sync at higher revs. So, I synced the carbs at 4-5k revs then took it back to 3k revs and damn it, the sync is out again. Sync at idle remained constant and even More mucking about to find the problem.

check your valve clearances. if the vacuum is going out of whack at a higher RPM it can be a sign that the valves aren't playing the same on each cylinder.