CB Carb woes

[Sir Fallsalot]

As I've posted before i had the carbs off the Big one a month or so ago to sort out the shit that got into the carbs and after putting it back together it was running sweet again, but after leaving it stand when i fired it up next it started pissing petrol all over my garage floor so yesterday i started the arduous job of stripping the carbs out again and found this red shit in the fuel lines

You can see it in the hole where the fuel enters the carb in this photo

This however had nothing to do with my leak it just happened to be in the holes where i needed to fit the new O rings on the T piece that the fuel pipe attached to so in one way it was a good job it leaked. After putting everything back together i had developed a new problem, when i revved the bike the revs wouldn't drop back down unless i held the throttle shut. This baffled me for a while and then i noticed that two of the carbs were not shutting all the way when i released the throttle. The carbs are in pairs with a link to join the two pairs together. When i split them down to replace the O rings i accidently trapped a spring in the linkage when putting them back together and that was holding the two carbs slightly open. I hooked the spring out and then spent the best past of an hour trying to find it, bloody thing had landed between the swing arm and the engine anyhow here it is 

And this is where it should to be

So dreading taking the cards back off i thought i would have a go at getting it back in with them in place and i got it in after a few minutes faffing about what a bloody relief i really didn't want to remove the carbs again

Because i had to back off a screw to get the spring back in it meant i had to try and balance the carbs and with only a two cylinder carb tune it wasn't going to be straight forward. The idea is the carbs are in pairs so i balance the pairs on cylinders 1 and 2 and then 3 and 4 first. Then i have to balance cylinders 1and 4 which will then balance all 4 carbs if that makes any sense 1 and two were a bit out but 3 and 4 were almost spot on

1 and 4 were way out which was what i was expecting as that was the adjustment screw i had to back right off to get the spring back in and when i dialed them in i had to drop the revs over a 1000rpm to get the tick over back so i think they were out before i started messing about.

seems to be pretty good now but going to borrow a 4 cylinder carb tune to check it before i put it all back together to finish the job off properly 

 

[XTreme]

13 minutes ago, Sir Fallsalot said:

The idea is the carbs are in pairs so i balance the pairs on cylinders 1 and 2 and then 3 and 4 first. Then i have to balance cylinders 1and 4 which will then balance all 4 carbs if that makes any sense

[Grasshopper]

Why did I enjoy reading that so much?  

I used to love working a carburettor.  That was the first thing I did on my old Honda.

[boboneleg]

I only have one bike left with a carb, the others are both injected.  Seems strange to me but it's the way of the world now.

[boboneleg]

Can't say that I disagree Bruce. 

Good work with the spring Fred, Taking carbs apart and overhauling them is very satisfying like Bruce says but fitting them back in usually involves skinned knuckles and a few expletives.

[Pedro]

I hate carbs, and fuel injection, I just want stuff to work with no problems. Ride along the motorway perfectly, climb a mountain pass to 3000 meters with no hiccups, back down, tick over at traffic, I don't need a personal relationship with my fuel system.

Every time I did carb stuff on the XR it took ages  

Having said that, last time I put the baffle back on and adjusted the air screw for it, it did feel rewarding. Don't want anymore, though. I do wish I was the kind of guy that confidently does that, but I don't think I am.

[Sir Fallsalot]

3 hours ago, Clive said:

Working on most parts of a bike came from necessity, bike shops around here were few and far between, a case of fix it yourself.

I like tinkering with mechanical things, the things I am confident with, and not end up fucking up something completely.

Lots of places to get the bike worked on around here i'm just too tight and i used to enjoy it but i am in Pedro's frame of mind now i just want stuff to work, I'm thinking of getting rid of the CB this year so i want it to work right but working on it makes me want to keep it 
Going to have a look at the cam chain tensioner next as they get a bit sticky on them at about 50000 miles and this bike is just past that and gets a cam chain rattle now and again fixed by stopping the engine and restarting 

 

[XTreme]

3 hours ago, Clive said:

I like tinkering with mechanical things

[Sir Fallsalot]

55 minutes ago, Clive said:

@Sir Fallsalot I was meaning when I started out in my riding career, nearest bike shop was about 12 miles away, and did not have the best reputation for their mechanical abilities, in fact they had a bad reputation.

I was also talking about when i started riding, there were some great mechanics about then not so much now as their either retired or dead and bike shops now seem to change parts until the problem is fixed instead of diagnosing whats wrong first 

 

[XTreme]

3 minutes ago, Sir Fallsalot said:

there were some great mechanics about then

Oh yeh......fix anything with whatever came to hand.....in  spit and sawdust shops!

[Pedro]

I really don’t think 12 miles is very far at all for a bike shop

[Sir Fallsalot]

I've moved to the cam chain tensioner tonight. first job was to remove the cooling system thermostat and fill point relatively simple job which involved undoing some jubilee clips and then covering my garage carpets and socks in antifreeze ffs. after moping everything up and  a clean pair of socks this is what i took off

 Removing that lot gave me better access to the rocker cover looks a bit scary in there i don't think I've done this to a twin cam engine before

Didn't take long to get at the cam chain tensioner and only had to remove one of the camshafts. But you have to remove the two R clips and push the pins out to free it from the cam chain while over the cam chain tunnel what could possibly go wrong 

Got it out without dropping anything into the engine but still have to put them back in tomorrow

From what I've read the bottom cylindrical part of the cam chain tensioner in the photo below is full of oil and stops the cam chain tensioner plunger from returning once the spring advances it, but when you drain the oil from the bike that part never gets drained and it gets a bit sticky usually around 50,000 miles. So the whole point of this exercise is to flush it out and refill with new oil because as far as i'm aware the oil has been there from when the bike was new which makes it 28 years old.

Last photo with the cam out really not looking forward to putting this back together tomorrow might have to get the workshop manual out looks a bit complicated 

 

[XTreme]

[Sir Fallsalot]

Got the engine back together tonight also adjusted some of the valve clearances which was quite time consuming without the proper tool for the job so just the rocker cover to go on and refill the cooling system tomorrow and then i'll find out if my efforts were worth it 

@Bruce the crows foot worked great for torquing up the cam sprocket bolts, would have had to remove the cam covers to do it with a socket 

 

 

 

[Tym]

Wouldnt be easier to buy a new bike? 

[boboneleg]

Nice work there Fred, I've never worked on anything more than a twin , I don't really like multi cylinder engines.  I'm slightly confused about one thing, you say that the oil hasn't been changed from new (28 years) , so does the tensioner run in a seperate oil bath to the engine ?

[DesmoDog]

On 15/02/2021 at 17:46, Sir Fallsalot said:

I've moved to the cam chain tensioner tonight. first job was to remove the cooling system thermostat and fill point relatively simple job which involved undoing some jubilee clips and then covering my garage carpets and socks in antifreeze ffs. after moping everything up and  a clean pair of socks this is what i took off

 Removing that lot gave me better access to the rocker cover looks a bit scary in there i don't think I've done this to a twin cam engine before

Didn't take long to get at the cam chain tensioner and only had to remove one of the camshafts. But you have to remove the two R clips and push the pins out to free it from the cam chain while over the cam chain tunnel what could possibly go wrong 

Got it out without dropping anything into the engine but still have to put them back in tomorrow

From what I've read the bottom cylindrical part of the cam chain tensioner in the photo below is full of oil and stops the cam chain tensioner plunger from returning once the spring advances it, but when you drain the oil from the bike that part never gets drained and it gets a bit sticky usually around 50,000 miles. So the whole point of this exercise is to flush it out and refill with new oil because as far as i'm aware the oil has been there from when the bike was new which makes it 28 years old.

Last photo with the cam out really not looking forward to putting this back together tomorrow might have to get the workshop manual out looks a bit complicated 

 

CAMCHAIN? We don't need no stinkin cam chain!

[Pedro]

4 hours ago, boboneleg said:

Nice work there Fred, I've never worked on anything more than a twin , I don't really like multi cylinder engines.  I'm slightly confused about one thing, you say that the oil hasn't been changed from new (28 years) , so does the tensioner run in a seperate oil bath to the engine ?

No, just that the tensioner is pushed by a dead end oil channel, as since it's a dead end the oil at the end doesn't get freshened up with the running engine or oil changes.

[Sir Fallsalot]

5 hours ago, boboneleg said:

Nice work there Fred, I've never worked on anything more than a twin , I don't really like multi cylinder engines.  I'm slightly confused about one thing, you say that the oil hasn't been changed from new (28 years) , so does the tensioner run in a seperate oil bath to the engine ?

As a rough description the part I've circled in the photo has a plunger in it which is pushed up by a spring and the space below it is filled with oil as it advances when the chain and guides wear, The oil stops the plunger from moving back once its advanced so keeps the chain tight, the oil in this part will only come out if you turn the tensioner upside down. New oil runs over this part when the engine is running but it does not replace the oil that's in there so hoping cleaning it out will fix it otherwise it's £150 for a new one

[Sir Fallsalot]

I'ts alive. I don't normally like first time startup videos as i feel it jinxes things but i did it anyway and sure enough i was jinxed got a ohh noo  feeling when it wouldn't rev and cut out  my temporary fuel tank was empty so all's good 

With fuel in it seemed to run better  sounds real quiet and ticks over so much smoother, it used to have a lumpy tick over i'm thinking the carb balancing has fixed that, hopefully it will still be ok after a run

 

[XTreme]

Sounds nice Fred! 

[XTreme]

39 minutes ago, Bruce said:

Tosh, I can hear overpressure in the crank. Better get that seen to Fred

 

[DesmoDog]

8 hours ago, Bruce said:

Mind you. Setting the backlash on those puppies is certain to make you shit while you cum.

Nah, it's not that bad. You just have to get the stepless plane on the crank/central shaft pair right first, then build from there. So all you need is time. And of course shims. And the tool to pull the bearing cups to replace the shims.

And remember to install the central shaft before putting the case halves together. And then set the stepless planes on the cams. And don't go back to tweak the main gear later cuz if you do you have to redo everything above it. 

And make sure you get the timing right, keep in mind the timing dots only line up once every six revolution. That assumes you aren't changing the cam timing, which you really should do because from the factory they're notorious for being off. And to change the timing you'll be offsetting the gears from stock settings, both top and bottom. Which means the factory timing dots won't line up anymore. Break out the timing disk. Youll probably want to add your own dots when you're done, though who knows if  they'll stay there. Or if the next guy to work on it will know what they mean. 

 

But other than that it's pretty much like using a chain. 

[boboneleg]

Nice work Fred, you've done a grand job there.  Loving the exhaust extractor as well

[Catteeclan]

Workshop meets were a regular thing on the TDM forum before covid. Good times.