750 jet size?

[atrent]

My daughter has a 1983 shadow 750. We have done some work to get it running much better than when she got it but it still has some issues. The installed jets are 120 and 40 both carbs. is this acceptable? We are at 600ft asl. There is some hesitation from idle to mid rpm. It is not very happy about starting in cold weather and I am considering doing the wire and relay mod to help reduce voltage drop at the coils. I will do it a bit different than what I have seen. Eliminating the extra fail point caused by the relay being in the circuit continuously. The relay will only be energized during start while the starter is engaged Has onyone have some comments on the wire mod? Is it worthwhile?

[93gc40]

First all, Shadows tend to be cold blooded. They like lots of choke at start-up. Especially if temps are below 60F. 120 jets sound about right, what does the manual call for????? Is the hesitation when cold or all the time. Have the carbs been cleaned and adjusted, pilots, chokes, idle and sync? Are the filters clean? Are the throttle cables adjusted? What happens if you add choke or give it more throttle? Results should not match.

[atrent]

Originally Posted by 93gc40

First all, Shadows tend to be cold blooded. They like lots of choke at start-up. Especially if temps are below 60F. 120 jets sound about right, what does the manual call for????? Is the hesitation when cold or all the time. Have the carbs been cleaned and adjusted, pilots, chokes, idle and sync? Are the filters clean? Are the throttle cables adjusted? What happens if you add choke or give it more throttle? Results should not match.

I am ticked off, just spent 5 minutes typing a reply and more info went to send it and I had been kicked off. I suppose for taking too long. I wouldn't mind that so much but my message has vanished as well.
Any way I can't find any reference to jet size in the honda manual. The carbs have been off and dipped in berrymans etc. Air screws have had the o rings replaced. Tje ground connections were inspected and cleaned up some were loose and even had paint under them. Replaced the battery with one of higher cranking amps These changes helped a lot in the starting. Improved from no start to start reluctantly.The rpm was hunting air leak style so I removed the carb boots from a spare engine that we have and installed them on the running bike. This stopped the hunting so I have purchased and installed new ones. It has not run yet because I don't want to replace the tank until I decide about doing the wire to the coil mod. I would really like to hear frim someone who has done this before I fo further. best post this before I get the boot again

[mattyo]

The clymer has #115 and #40 shown for the 83 vt750 but when I rebuilt my carbs they had #118 and #40. Have you sync'd the carbs? I noticed much better response at low rpms after re-syncing. Chances are they haven't been sync'd in 30 years.

Are you running with stock exhaust? My bike has aftermarket pipes and it would pop on decel quite a bit so I sized up my slow jets to a 42 and 45. My rear cylinder was a bit stubborn. Come to find out, the oil ring around the piston was bent so I'm assuming a bit of oil was mixing in my combustion chamber. Long story.

Vacuum leaks around the boots are also problematic but it sounds like you found that problem already. I would definitely re-sync the carbs after putting the new boots on.

As 93gc40 said, the 83 does not like cold weather, well not even "cold". My bike doesn't even like to start if it's below 70F. It's a stubborn old man! Make sure the enricher works properly because the bike will start much better with a working enricher. There's a little trick a few of us have stumbled upon to get this bike started more easily. Give it about 1/3 enricher, push the starter button and when the engine fires up, leave the starter engaged and then slowly increase the enricher to about 2/3 to 3/4, and then release the starter. This seems to be a characteristic specific to the 83 vt750. Very strange, but it works like a magical leprechaun dancing on rainbows.

Assuming you have stock exhaust and you're not getting any popping on decel, I'm guessing that if you put new boots on and re-sync you'll get a very noticeable improvement at low rpms.

I know your pain about losing a long post to cyber-space. It's happened quite a few times to me. I write too much and take too long. So now I copy my long posts before sending it and if it get's lost, which still happens quite a bit, I just paste it back in. They should really increase the "inactivity" time limit on this forum. Oh well.

And get a pic of the bike up! I love seeing the old 83's still up and running!! Okay, it's not that old, but I have an 83 so I like seeing other 83's!

[mattyo]

Originally Posted by atrent

It has not run yet because I don't want to replace the tank until I decide about doing the wire to the coil mod.

Glossed over that sentence the first time.

Do you mean putting the fuel tank back on or actually replacing the fuel tank? I haven't done the relay mod but from what I've read from others, it doesn't give any "significant" performance boost. It's just a nice mod to get some extra voltage for the coils (slightly hotter spark in theory) and eliminate the fuel relay, which sometimes is a problematic component. If you like doing mods and little projects like this, than go for it. It can't hurt. If the fuel relay is working, and you don't want to deal with another little side project, I'd just leave it be and deal with the more urgent problems first. Just my 2c.

[atrent]

Originally Posted by atrent

My daughter has a 1983 shadow 750. We have done some work to get it running much better than when she got it but it still has some issues. The installed jets are 120 and 40 both carbs. is this acceptable? We are at 600ft asl. There is some hesitation from idle to mid rpm. It is not very happy about starting in cold weather and I am considering doing the wire and relay mod to help reduce voltage drop at the coils. I will do it a bit different than what I have seen. Eliminating the extra fail point caused by the relay being in the circuit continuously. The relay will only be energized during start while the starter is engaged Has onyone have some comments on the wire mod? Is it worthwhile?

An update on starting problem. The jet sizes are what are called for so we will forget that for now. I did install the bypass relay so that the power is delivered directly to the ignition during cranking. So far the results have been extrenly favorable. Even on the cold spell we had it starts up after about 2 revs. So far very pleasedwith the result. I have installed the relay so that it is only energized while cranking. My problem now is how do you get at the carb eqilizer adjustment without buying some fancy tool?

[atrent]

Originally Posted by atrent

My daughter has a 1983 shadow 750. We have done some work to get it running much better than when she got it but it still has some issues. The installed jets are 120 and 40 both carbs. is this acceptable? We are at 600ft asl. There is some hesitation from idle to mid rpm. It is not very happy about starting in cold weather and I am considering doing the wire and relay mod to help reduce voltage drop at the coils. I will do it a bit different than what I have seen. Eliminating the extra fail point caused by the relay being in the circuit continuously. The relay will only be energized during start while the starter is engaged Has onyone have some comments on the wire mod? Is it worthwhile?

An update on starting problem. The jet sizes are what are called for so we will forget that for now. I did install the bypass relay so that the power is delivered directly to the ignition during cranking. So far the results have been extrenly favorable. Even on the cold spell we had it starts up after about 2 revs. So far very pleasedwith the result. I have installed the relay so that it is only energized while cranking. My problem now is how do you get at the carb eqilizer adjustment without buying some fancy tool?

[tubes_rock]

I bumped my slow jets to a 42 even with stock exhaust and it helped get rid of a flat spot. Also, turning the idle pilot screws out to 3.25 turns helps with a little low-end hesitation.

You can build a comparative vacuum gauge, called a manometer, for less than $5.

Follow this thread:
Manometer

--Justin

[atrent]

Originally Posted by tubes_rock

I bumped my slow jets to a 42 even with stock exhaust and it helped get rid of a flat spot. Also, turning the idle pilot screws out to 3.25 turns helps with a little low-end hesitation.

You can build a comparative vacuum gauge, called a manometer, for less than $5.

Follow this thread:
Manometer

--Justin

I guess I should started a new thread. Anyway my problem is not the manometer but getting at the equalizer adjustment screw. It is a 7mm hex head and also has a slot for a straight blade driver. I have a 7mm box wrench but the screw is in such a location as to be near impossible to get at. I wonder if Ican set up the pilot screws with the air box attached and then remove the connecting duct so the adjusting screw becomes accesable. Any thoughts on this?

[tubes_rock]

Ah! Yeah, that was a bugger.

I made the tools I needed. I used a 1/4" piece of rod and cut it into several pieces, bending each one into an "L" shape, like an Alan wrench. Then I used my bench grinder to grind a straight blade point onto each one, but with each one at a different angle. Then i used one to turn the screw 1/8 of a turn until i couldn't go any more, then got the next one, with a different angle ground into the tip for the next 1/8 turn, then got the next wrench for the next 1/8 turn. I think I made 4 of those, and that gets you 1/2 of a turn, and then you can start over with the first wrench again.

Honda makes a special tool for it, but it's something like $70. Forget that.

--Justin