HELP bike keeps dying on longer rides

OUCH

 

Alright another update,
I was able to find a replacement starter on FB that allegedly works. I will be double checking and may rebuild.

I tore into own of the carbs and started checking numbers. Everything matches except the main jet and pilot jet.
Main Jet: 115
Pilot Jet: 32.5
I have stock exhaust and a KN filter, altitude 1000

 

The other three pilot jets aren’t marked, is that normal?

 

Sounds like someone re-jetted it at a previous time, although they went the "wrong way" on the pilot fuel jet (stock size is a #35). Of course this assumes they are actually Mikuni jets, which have a funny little "squares within a square" symbol on them. Un-marked jets = aftermarket, and for some aftermarket jets (like those that come with "power" kits), the inscribed sizes aren't really comparable to stock jet sizes, since the aftermarket manufacturers use their own "sizing" specs.

 

The other pilot jets? should only be the two down in the float bowl, for the 750 they are #120 mains and #40 for the pilots from the factory, I've stepped up to #126 for the mains and #42 pilot. There are two jets under the lid/diaphragm that I don't recall having being addressed on the forum. If they have and place back in the carburetors according to the service manuals they are in the WRONG positions, both the factory and Chiltons manuals have them transposed so you might want to check them out just to make sure.

 

Apologies, by other pilot jets I meant the other three carbs. 1 marked as 32.5 and the other 3 with no markings at all. I checked the one under the diaphragm (I only see one) in one of them and that was size 165 which is the correct number for my 550. I should probably check the other three carbs to be safe. But I will be purchasing Chacal approved jets along with all the other parts I need. Going to do a valve clearance check next and hunt down a welder for my collector box. I should be riding again soon. I also just got a new iPhone and might try my hand at making a video of all the things I fix and check

 

Ok so I put it all back together, paper air filter, stock jets, working starter, rebuilt petcock/gas cap w/ inline fuel filter and vacuum hose attached to third carb boot.

once the fuel worked its way through the carbs I was able to get it running with the choke on but it died once that was off. Currently air mixture screws are 2.75 turns out from bottom.

the question is, do I need to mess with the air mixture screws and the idle knob to be able to run it without choke or am I missing something bigger?

 

short answer: yes. They all work in concert.

 

Thanks for the short answer, I figured since the carbs were working as best as they could that it was unlikely they had a clog somewhere, I took them off the bike, drained them and replaced two jets per section.

sequence of tinkering should be: idle screw until I can idle with the choke off, then color tune and synch the carbs to the engine? Repeat until just a smidge above Bunsen blue and manometer levels are all equal

 

Issues with idling attempted to turn the idle screw clockwise.

I am unsure if my petcock is working properly. It will pass gas when on prime and doesn’t when ON. Which to my understanding means it is working. But as I have been trying to work on the idle problem the fuel doesn’t appear to be filling the line while “ON”

 

Thought it was flow in PRIME but needed a vacuum signal (taken from #3) to actually open the valve in the ON position. I'm running an aftermarket fuel petcock (ON/OFF/RES) as my original was leaking and I didn't have the patience to rebuild it... someday I might as it's still in the bottom drawer.

 

#3 as in carb manifold 3? I thought so too but in my clymer it referred to removing the vacuum hose from the second manifold.

 

I think I may just have to test for leaks on the boot and then take the carbs off and give them a cleaning I took them to church a while ago and replaced all the seals and o rings. Clean the passages with carb cleaner and wire let the jets soak overnight, compressed air all that jazz. Should have just cleaned them before putting them back on!

 

Ok so I took out all the jets and gave them a cleaning with carb cleaner, water, water/pinesol bath in an ultrasonic cleaner. Used an air compressor and small wires to gently clean the passage, same with the carb rack but I did not break it apart. The pinesol/water ultrasonic did cause some of it to rust. I used a wire brush and wd40 on the rusted parts until they moved without sticking or creaking.

petcock looks good since it was off the bike and didn’t leak a drop

I have the air mixtures at 2.5 turns out and the bench synch looked pretty consistent between the 4

I now have the opposite issue!!! I initially had to get it to start on choke but now it doesn’t need that. HOWEVER!! It instantly turns on and revs to 4-5k rpm!!! when I rev the throttle it responds and doesn’t hang but I keep turning out the idle screw and not feeling like it is working too well. It’s possible some of the wd40 was on the carb boots. I had to take them off when I realized I forgot to attach the gas line

 

So I got restless, took the air compressor and sprayed off all the excess wd40 and let the bike run. It came down eventually and now wont idle without the choke.

so either:
1. there was excess wd40 within the system that eventually used itself up
2. I did not readjust the idle knob and it is completely backed out causing the fly’s to be completely closed
3. Air leak somewhere… manifold or throttle shaft seals, both of which have been replaced during this project

more to come later.
I know I am so close to cracking this!!!

 

https://youtube.com/shorts/wap9CuOmXCs?si=-ZDJ1xKu6mw5QIW-

Why is my bike sounding like this?

 

Sounds like an exhaust leak at one of the front ports. Grab a 2-foot length of garden hose or similar and hold one end to your ear while moving the other end around the front pipes & ports with the engine running listening to the crackling and popping sound, it will stand out when you zero in on it.

 

So I had forgotten to tighten the nuts of the exhaust to the head, torqued those to 10n/m as the clymer stated. I will test again tomorrow and update

 

So the bike is definitely not as erratic, still can’t get it to idle with out choke. I plan to turn the mixture screws out a half turn (3 full turns total) and try again tomorrow. I ran into an issue when priming the carbs that gas leaked from the air box. I assume a float must be stuck, I reached in and it was only coming from carb 1. I stopped priming and gave it a couple of whacks with my mallet. Hopefully that fixed it. Bought some starter fluid to test for air leaks as well

 

Ok so carbs are off and currently hooked up to a free flowing source and not leaking gas all over my garage. When I took them off and looked inside number 1 the float was freely moving but the metal wire of the float needle that interacts with the float tang seemed askew so my guess is that was the cause. I took 2500 grit sand paper to the pin that holds the float and the area it passes through just incase it was catching. Feels a lot smoother now and I bent the tang responsible for how far it drops not the one that sets the fuel level. Letting it sit for three hours to make sure it works, then back on it goes.