Colortune hard to reach yellow, possible suggestions?

I got this bike last fall and have pulled the carbs twice. The last time I found some slight additional dirt (even after the last cleaning and adding an inline filter) in the furthest left bowl. I think because of the way the bike leans when on the stand.

I also shined the plungers (passing the 'clunk' test I did not know about the first time), and made sure to extremely clean the pilot feed and hole in the bowl to feed the pilots in each bowl.

After reassembly my bike starts excellent using just the choke, where before it was hard work using carb cleaner. I set all the mixture screws to 1 3/4 turns and it idles fine, but would backfire sometimes when revving (other times it would sound great and take throttle fine).

I bought a colortune and had 1 that would not produce any flame at all (2nd in from right), checking the header it is cold. The others it was hard to see but I think there was blue flame, after lots of adjusting I could get yellow to show, but I am talking about 4-5 turns out and this is a 1980 that should have the coarser threads. That's a lot.

Still it is what the colortune said and when giving throttle I could clearly see blue and then yellow when throttling down and it sounded and idled great (although only on 3 cylinders). Driving around the yard it basically had no power and would not take throttle under load, could just be because it was running on 3 cylinders, I don't know.

I recently found mention of the throttle shaft seals in a post by Chacal and also the outsides of my rubber intake manifolds have some cracking in places, so I again tried propane all around the carbs. This produced no revving or smoothing or change at all to the idling. I then sprayed starter fluid all over the carbs specifically on the manifolds and throttle shaft seals and again, saw no change in idle.

Pulling the carbs I found the 1 carb that wasn't running had a lot of fine red sand in the main jet and that the pilot hole was not feeding in to the pilot jet, even though I just cleaned this. The other carbs are spotless.

So I am going to get 4 new mixture o-rings (2 were missing) and try the HCP4024 that Chacal sells, plastic shim washers that are supposed to make adjustment easier (although I just re-read this and see this might be actually talking about the long idle screw and I previously thought these were for the mixture adjustments).

I was planning to replace the throttle shaft seals, but since spraying didn't result it anything is it worth the time to replace them? I expect they're not actually bad.

Are there any other spots that could be leaking vacuum? I'm hesitant to declare the intake manifolds 'bad' due to the cost to replace them and because they do not have any obvious leaks. Is 4-5 turns ok for mixture adjustment on a 1980 Maxim? I have seen posts talking about 4 turns from factory but was pretty sure these were the newer Maxims with finer thread. I would think I am talking about 8 or more turns if these were the finer thread. For comparison about 6 turns and they're completely out and can be removed, so I'm right at the limit of adjustment.

Any other suggestions?

 

Are your valves in spec?

 

They aren't but they aren't that bad. 2 ex valves are a little tight and 2 intakes are very tight, waiting for my bucket holder tool to remove the shims and use the chart to get the correct replacements.

One of the carbs (2nd one from left) had the same issue with Colortune, requiring almost fully out mixture screw and its valves are right on spec.

I have seen in other bike forums mention that if your float level / gasoline level is too high it could lead to a mixture richer than the mixture screw can correct for. I'm having trouble seeing any flame, much less yellow, so I don't think that is the issue, but wondering if anyone has run in to anything else affecting their tuning.

I guess I should at least do my V-SEALS to be sure, but with no response from the bike to propane or starter fluid I feel like I'm barking up the wrong tree.

 

First things first, you HAVE to get the valves in spec, or anything you do is barking up the wrong tree. No adjustment will work correctly until you get that done.

 

To comment on the shim tool...

Personally I found the shim bucket tool not worth the hassle... Some people might frown on it, but I just used a piece of insulated wire (heavy gauge) to hold it in place (going in via the plug hole). Much easier and you don't have to turn the engine backwards to remove the tool.

PS: Update your sig so we know what bike you have; makes it easier for the gearheads here to provide info