Bike won't restart after warm?

I tried searching, but I'm afraid I haven't found the right combination of words to find an answer to my issue!

I just finished replacing the coil (with WG coil mod), cleaning the points, setting timing, and cleaning/rebuilding carbs. It went from not running at all, to starting on the first kick this morning!

Anyhow, after riding it for about ten/fifteen min I stalled it taking off from a light, and I couldn't get it to start for 5 min or so. Started again, and then then stalled it again about 20-30 min later, at which point it wouldn't start for even longer! I couldn't for the life of me figure out what the right combination was other than a random period of time, and LOTS of failed kick starts. Is this a possible spark plug issue? The plugs are somewhat fouled with carbon, but I don't know if that is related...

Thanks again for helping! You guys are single handedly returning a much abused bike to its former glory!

John

How old is the battery? Ed

Valve clearances been checked? All Battery cables clean and tight? Alternator output been checked?

Battery is pretty new, and checked that it's holding 12v. Alternator is ok. Have not checked valve clearances yet though! I guess that will be next on the list to look at.

I replaced the plugs today, going on the idea that it may be a correlation /= causation issue: IE. fouled plugs by running on the choke too long, then was hard to start, and it just happened to be when the bike was warmed up.

I did notice that when I switched them today that one of the ones I had cleaned yesterday was looking pretty good- some carbon on the top and exterior, but clean on the ceramic interior part, but the other one was pretty fouled with either carbon/gas or oil?! Really hoping that's a I'm an idiot and left the choke on too long issue rather than a blown piston ring or valve issue... Would the bike still run pretty well even if it was leaking oil into the combustion chamber? Because when it is running it runs fine.

Thanks for all the help, and I'll let you know how it looks after I check valve clearances and recheck plugs in a bit.

"carbon/gas or oil"... Carbon is dry while the other two will be wet plug @ the tip... Which one on your plugs?

Let's start with some basics here since I'm old & stupid...

All stock or performance engine, camshafts, 4-1 exhaust, baffles, air box or pods, Stock or EI, valve clearances, head valve job/P&P etc....

What engine and carbs are we speaking of here?

What jets are presently installed if known?

What pilot screw settings are you at presently?

WG coil mod.... arrrrgggghhhh :whistle: ... you're positive you have +12Vdc or greater feeding into the coils?

OMR

coils could be getting hot,
could be cracked and as they heat up cracks expand and coils stop.

points if it has them could be closing up when hot,

fuel filter could be blocked or a fuel lock in line.

recheck coil mod wiring.

im not a mechanic im a carpenter,

"im not a mechanic im a carpenter,".... :blink:

Old Man Rock wrote:

"im not a mechanic im a carpenter,".... :blink:

tough crowd :blush:

If only I could fix my bike with a good set of chisels and a planer- I wouldn't be in this mess.

Sorry for the lack of description on the bike. The engine is a 750cc twin, with the stock Mikuni BS 38 carbs. It's got pods, but stock jets, as the previous owner apparently decided that it wasn't worth following through the tuning needed for switching out the airbox (which he threw away ) I've got larger jets on order as we speak, and put the main jet circlip on the bottom (5th) notch as an experimental interim fix- I'm not convinced it's done any help, but it probably hasn't hurt. It also has a MAC two into one exhaust. Other than that, everything is stock.

I still haven't checked valve clearances yet, and to be honest, it won't be until next weekend that I get a chance to- I've already borrowed more than my allotted wrenching time for this weekend, and need to get back to my real world duties! Valve stuff is also a new experience for me, so I'd like to take my time doing the checking.

I checked all the connections from the coil mod, am getting 12v to the coils, which are a new set from Z1. Points are still old, but I cleaned them up best I could, reset the gap, and set the timing using the static method described in the service manual. Judging by the readings from the multimeter I think the points are actually ok mechanically, even if they do look a bit dilapidated. Regardless, I've got a set on backorder that will go in once they arrive.

I just went out and ran the bike for 10 miles or so on the new plugs, and it actually seems to have helped/solved the issue of starting when warm, I turned it off about 3/4 of the way through and she started back up on the first kick. I plan to see how she does for the rest of the week before I start messing around with anything else.

I also checked the plugs again when I got back and both were a nice light brown colour, with some indications of being a bit lean on the tab. No wet buildup on either one. All and all, I think I'm fairly happy with current set up until I get the larger jets in that match the pods and exhaust.

Thanks, and will have to start a new post next weekend to update on the latest saga!

John

"Points are still old, "... do yourself a favor, replace with new points and condenser... Could be breaking down with heat....

Good luck... Keep us posted on your findings...

OMR

OMR-

Agreed! Both new points and condenser are on the way, just waiting for Z1 to get them back in stock (apparently I'm not the only one that needs new points!).

Thanks so much for all the advice, and I'll be sure to keep everyone updated.

Best wishes for the rest of the weekend.

John

johnAB wrote:

Anyhow, after riding it for about ten/fifteen min I stalled it taking off from a light, and I couldn't get it to start for 5 min or so.

That always makes me wonder if the gas cap vent is clogged..... but only because it happened to me and it's something you never forget.:laugh:

You might throw your timing light in the carrier and check for spark when the engine won't start. Electrical things do start screwing up when they get hot.

BTW, here's something every B owner needs to remember: if you foul EITHER plug, neither one can spark so you will not have any spark at all when you check but it may not be an ignition problem.

I would also carry a set of spare plugs and a wrench: when it goes dead, quickly install the backup plugs and see if it fires. Sometimes a plug will foul and not look that bad to the eye... another thing I learned the hard way.