HARD starting 750

[hikermikem]

Well I've gotten my "new" 81 750L running (16V), & it runs really well.

Stock airbox & exhaust - no mods at all...

Work performed:

Dipped & cleaned the carbs.
Adjusted the valves.
Sealed the stock airbox - new K&N drop in.
Raised needles .030"
Upped main jets one size to 115 (from 112.5)
New head gasket
New base gasket
Replaced coils with another stock set (from my 850) with NGK caps
New petcock
Cleaned & coated the fuel tank with POR-15

Had to shoot some gas into each cylinder to get it started, but after warming it up I adjusted the mix screws in each carb (highest RPM), & vac sync'ed them as well. A quick run up & down the street showed great promise, pulls very hard but has some popping on deceleration.

MY problem?? It doesn't want to start. If I shoot some gas in the intake vac ports she'll fire right up.

Today, I remembered reading here about blowing into the vent hoses sometimes helps... I'll be pickled & jar'ed if that just didn't work!! It started after that, but not like the gas trick...

Anyway, for those of you that have had the same problem, what did you do to fix the hard start issue??

Any & all suggestions welcome.

Mike

[Larry D]

Mike, why did you raise the needles and go up one on the mains, if everything else is stock ?

How does the spark look ?

[hikermikem]

Mike, why did you raise the needles and go up one on the mains, if everything else is stock ?

How does the spark look ?

Hi larry,

I always raise the needles a notch or so to improve the mid-range on these very lean bikes.

The mains went up a size (112.5 - 115) because I needed a new main (one of the originals craped the bed on rebuild) and I had the 115's hanging around from a previous rebuild. Also, I figured with the K&N drop in it wouldn't hurt to go up a size.

The issue is getting this beast started - been a bear to start but once started it runs very well... lot's of power through out the entire range.

I see you have the same bike - do you like it?? I've not messed with one of these yet.

Mike

[Nessism]

Hey Mike, Go out and run the engine hard for a few hundred miles. Call in sick to work and go ride instead. Hopefully, after a few hundred miles the engine will start to behave better - often times the compression will increase after a good flogging (Tkent trick).

[chef1366]

Did you make sure the choke tube that goes into the float bowl was clear and also the jet in the float bowl that the tube goes into.

[hikermikem]

Hey Mike, Go out and run the engine hard for a few hundred miles. Call in sick to work and go ride instead. Hopefully, after a few hundred miles the engine will start to behave better - often times the compression will increase after a good flogging (Tkent trick).

That's a great idea - unfortunately I have to be in TX all next week so that's not an option

Also. I'm currently rebuilding the front brakes, as they are just plain neglected & STUCK...

[hikermikem]

Did you make sure the choke tube that goes into the float bowl was clear and also the jet in the float bowl that the tube goes into.

Yes, I did - I'm pretty anal about making sure ALL the little tubes/passages are clean & clear...

[hikermikem]

bump - anyone?

[posplayr]

Did not read the whole thread, but have you measured the voltage to the coils when the key is on. If it is 9V the bike will be real hard to start. The Coil relay Mod can get you back over 11V and startup is vastly improved.

Start by doing a hardwire from the battery to the Orange/White wires at the coil and see if it improves. If so U know what U need to do.

[almarconi]

I too am dealing with the exact same issue on my 750L. First start of the day involves a small puff into the breather hose. Then bike fires up fine.

I've been chasing this problem for a while. Blowing into the breather hose in effect primes the engine. When the engine is cranked over and the enrichener circuit is active, fuel should be drawn into the combustion chamber. I have been able to get the bike to start if I close the throttle butterflies all the way by turning down the idle knob. Obviously the bike stalls almost as soon as it starts because the idle is set too low. This leads me to believe that my carbs may need to be bench synced again.
I just vacuum synced them and they seem to be pulling about the same across all the carbs.

Another thought I had was that the fuel level is too low and I need to recheck float height. I had a hard time doing this because I have trouble seeing real close up. I was using a machinists rule and the scale is so small I could not distinguish the marks very well. I have a digital calipers on order that will measure the depth.

I also thought about bumping the pilot jets one size up to a 45 from the stock 42.5. I'll probably do this when I pull the carbs to check the float height. For all I know, some of the jets in the carb are not the size that are stamped on them.

I was able to start the bike tonight by just bumping the starter. Literally press the button for 2 seconds and the bike started right up cold. Didn't need to blow into the tube. Why this works I don't know, if you repeatedly crank the bike, it won't start. I've measure battery voltage and I'm only getting about 12.3 volts at the battery, 11.9 volts at the coils with relay mod. It could be my battery is weak. It's a 2 years old, walmart brand battery. Even when fully charged I have never been able to get the battery over 12.6 volts. The battery in my KZ reads between 12.9 and 13.0 volts at rest. I'm running accel coils and wires so its possible I'm not getting enough voltage to the coils. Once I get some spare cash I think I'm going to get one of the AGM Big Crank batteries.

I've talked to Tkent02 about this since he had a 650 that has the same symptoms. It could be problem with the way the carbs were manufactured. I don't have a spare set of carbs to see if this is the case. It seems either your bike starts effortlessly or you've got one that has this problem. Bike runs fine once started and will restart no problem its just the first start of the day.

If anyone has any ideas, I am all ears as this has me stumped. No amount of carb cleaning seems to fix the problem.

[goatboy]

82 750EZ similar hard cold start issues

I've had same difficult "cold" start issues with my 82 750EZ since I bought it in '87 from 1st owner at 5000 mile mark. If it's under 60 degrees F and hasn't been run in a day or two, AND if I don't get it started on 1st try (no matter the choke aka "enrichment" lever setting), then it's gonna need a squirt of starting fluid to get engine running. Starts fine once warm, regardless of ambient temperature.

Stock config, with 23k miles (although hard-start issue has existed since 5k mile mark when I got it.)

Rebuilt carbs w/ bench sync & GS site recommended vendor for gaskets & jets, new stator, new battery, new factory fuel petcock, new ND Splitfire plugs, Duanage's R&R fix (Thanks D!), fresh valve adjustment, new air filter/oil change, etc when I pulled it out of storage almost a year ago. BUT, this has been a problem since the day I bought the bike in 1987!

Bike always runs well/pulls like crazy (once it starts) throughout RPM range. (Realize that I probably need to check out plug wires, caps, and coils, BUT this is exact same problem I had when I got bike 22 years ago.
Starts with 1st push of starter button if "persuaded" w/ starter fluid if cold, but starts immediately if over 65 degrees F, or it's been recently ridden.

Not a major issue (IF I have a can of starter fluid with me at all times! when it's cool weather), but it's very annoying as I ride all year.

Other than checking, and possibly replacing coils, wires, caps, got any suggestions? BTW, compression is also well within specs.

[almarconi]

I've never needed starter fluid to get the bike running. BTW starter fluid is really bad for the engine. You may want to try the puff into the breather tube to get some extra gas into the combustion chamber. I thought spark was an issue so I upgraded the stock coils to the accels. It made no difference the bike still acted the same. I do need to try with a "hotter" battery to see if this makes a difference.

Hard starting cold is usually due to tight valves. If valves are in spec, have you tried richening the pilot circuit? Either 1 size on the pilot jets or opening the mixture screws may help.

[hikermikem]

Did not read the whole thread, but have you measured the voltage to the coils when the key is on. If it is 9V the bike will be real hard to start. The Coil relay Mod can get you back over 11V and startup is vastly improved.

Start by doing a hardwire from the battery to the Orange/White wires at the coil and see if it improves. If so U know what U need to do.

Yes, this approach seems like a reasonable first step...

I haven't yet gone through the electrical system completely & cleaned everything. I did just check the incoming voltage at the coils & it was about 8.5v !!

Seems a coil relay mod is in my future I guess.

I'll run the wire direct from the battery as you have suggested & see if that helps the starting to confirm.

Thanks for the reply.

mike

[Larry D]

Sounds like you may have found the issue Mike.

One of the first things I did to my bike was replace all the bullet connectors with spade types. Clean and shrink wrap them all. To be honest, I didn't do them ALL. I still have to get inside the headlight bucket.

[hikermikem]

Hi Larry,

Hopefully I've discovered the issue. I've done the coil relay mod on my 850 last year, and I guess I'll be doing it again. I bought several relays for spares so it shouldn't be bad...