Stalling at Operating Temp.

[Fire-medic]

The ignition coils often develop cracks with age, and in many cases, the issue does not affect the ignition operation.

What are the readings before and after the fan starts? I assume you didn't have any issues with the fan, screeching or anything, as it's not mentioned. A bad bushing/bearing on an electrical accessory can cause problems as the appliance works harder to overcome the increased friction.

 

[Screwloose]

do you have original caps

The original caps are very costly so it's seldom anyone changes them. I changed the caps (NGK alternatives) and leads and it done the trick.

 

[Fire-medic]

After doing some testing and looking around, I have a few observations.
1. The problems(drop in voltage and sputtering) occur when the cooling fan kicks on.
2. The pick up coil resistance was within the recommended range.
3. The primary and secondary omh readings on the rear ignition coils were high after the "shut off." Primary(3.8) Secondary(13.9k)
4. The front ignition coil nearest the left scoop has a hairline crack along the bottom.

The primary reading is high, the secondary is OK.
Primary: 2.7 ohms +-10% for a high of 2.97 ohms
Secondary: 13.2 K ohms +-10% for a high of 14.52 K ohms

 

[MadHatter16]

The original caps are very costly so it's seldom anyone changes them. I changed the caps (NGK alternatives) and leads and it done the trick.

I do have the OEM coils, caps and leads.

 

[MadHatter16]

The primary reading is high, the secondary is OK.
Primary: 2.7 ohms +-10% for a high of 2.97 ohms
Secondary: 13.2 K ohms +-10% for a high of 14.52 K ohms
View attachment 76425View attachment 76426

The fan runs pretty loud. I think it will be worth looking into. Because I went through the charging system and am currently getting 14v at idle and 14.5 at 2000 rpms. That is until the motor warms up and the fan kicks in. I did unplug the fan to see if that was the problem and it ran longer, but still stalled out.

 

[Screwloose]

I do have the OEM coils, caps and leads.

I had temp probs when the bike was sitting still at idle. Traffic lights etc. When temp gauge went above midway mark i would get idling problems big time, and then i would have to switch off and wait for engine cool down. I bypassed the fan sensor and put a switch in, changed the coolant, but the problem still went on. Then i noticed in the dark if you get to temp and run a bit of metal (screwdriver) round the leads and caps whilst being close to the body to allow an arc, then i got a few, but only at temp.

My theory on this is that due to the high cost of caps, and the leads being a bit awkward to change on the vmax, then nobody ever changed them. That was definately my problem, so i would say change them anyway, and the plugs.

good luck

 

[MadHatter16]

I had temp probs when the bike was sitting still at idle. Traffic lights etc. When temp gauge went above midway mark i would get idling problems big time, and then i would have to switch off and wait for engine cool down. I bypassed the fan sensor and put a switch in, changed the coolant, but the problem still went on. Then i noticed in the dark if you get to temp and run a bit of metal (screwdriver) round the leads and caps whilst being close to the body to allow an arc, then i got a few, but only at temp.

My theory on this is that due to the high cost of caps, and the leads being a bit awkward to change on the vmax, then nobody ever changed them. That was definately my problem, so i would say change them anyway, and the plugs.

good luck

What would you recommend for a replacement? I have read about COPS.

 

[Screwloose]

What would you recommend for a replacement? I have read about COPS.

I dont have cops, but the next time i’m in that area i will change to them. The reason i say that is i noticed the coils dont like getting to very high temp. Its a vicious Circle. At the time i just wanted to get it fixed as i had carb problems also. NGK do alternate caps, the ones in the photo are what i used. Not saying this is definately your problem, but it certainly was mine.

 

[Screwloose]

What would you recommend for a replacement? I have read about COPS.

Also next time i’m changing the coolant i’m going for waterless.

 

[Fire-medic]

COPS you kill 2 birds with one stone. Contact Sean Morley [email protected]

 

[one2dmax]

OK, to clarify. What does it do or not do when hot. It cranks fast and normal but won't start. OR, it cranks slow and hard. The latter is almost always an issue with an older starter (they improved the design in 90)

 

[MadHatter16]

OK, to clarify. What does it do or not do when hot. It cranks fast and normal but won't start. OR, it cranks slow and hard. The latter is almost always an issue with an older starter (they improved the design in 90)

It will usually crank normal after the "shutoff," and I can hear the cylinders firing. I didn't get a chance to test spark after the engine got hot. That'll be the next thing I test.

 

[Fire-medic]

OK, to clarify. What does it do or not do when hot. It cranks fast and normal but won't start. OR, it cranks slow and hard. The latter is almost always an issue with an older starter (they improved the design in 90)

It's a 1988. He should have both the 2-brush starter and the analog (early) ignition box. Along with the skinny fork downtubes/sliders, single-opposed pistons in the calipers, and the 'old' star shift drum.

 

[Screwloose]

It will usually crank normal after the "shutoff," and I can hear the cylinders firing. I didn't get a chance to test spark after the engine got hot. That'll be the next thing I test.

Same here, no problems turning engine over even after it shut off at temp.

Metered all cables at ambient temp and they were in/ very close to spec. (Remember and NUL your test meter leads before taking a reading).

Suggested theory is that elec cables and MOST items that carry current will heat up as poor ability to conduct increases (age and use). As the heat goes up the leads and caps become giant resistors, and hence produce more heat, and so the cycle goes on. It will damage your coils also as coils are not designed to supply high resistance heater elements. The current then tries to release somewhere, and as current follows the easiest path it will then arc to the nearest earth point, I.E. engine/frame. The fault (for me) was very consistent in that it will cut the bike out at almost the same temp gauge reading in every case over many months, and will restart at almost the same temp readings.

Again only what happened to me!

But if you have the original caps there will be a high percentage chance they are Kaput. I think The suggestion of COPS removes all the old crinkly/split crap that has been carrying current for many years, and removes the chance of having damaged the coils slightly due to temp. I think the introduction of COPS is a perfect choice for the Vmax G1 as the back cylinders heat up more than the front also. Heat reduces not just current flow, but destroys cables and connectors never to recover.

 

[MadHatter16]

Same here, no problems turning engine over even after it shut off at temp.

Metered all cables at ambient temp and they were in/ very close to spec. (Remember and NUL your test meter leads before taking a reading).

Suggested theory is that elec cables and MOST items that carry current will heat up as poor ability to conduct increases (age and use). As the heat goes up the leads and caps become giant resistors, and hence produce more heat, and so the cycle goes on. It will damage your coils also as coils are not designed to supply high resistance heater elements. The current then tries to release somewhere, and as current follows the easiest path it will then arc to the nearest earth point, I.E. engine/frame. The fault (for me) was very consistent in that it will cut the bike out at almost the same temp gauge reading in every case over many months, and will restart at almost the same temp readings.

Again only what happened to me!

But if you have the original caps there will be a high percentage chance they are Kaput. I think The suggestion of COPS removes all the old crinkly/split crap that has been carrying current for many years, and removes the chance of having damaged the coils slightly due to temp. I think the introduction of COPS is a perfect choice for the Vmax G1 as the back cylinders heat up more than the front also. Heat reduces not just current flow, but destroys cables and connectors never to recover.

It sounds like our problems are very similar. It would make sense seeing as how my charging voltages are good, but suddenly drop. I did a bit of searching and decided to get 7mm copper core wire along with the NGK Caps to see if it makes a difference before I get COPS. Also Sean Morley is out of them at the moment.

 

[user 16790]

new plugs, caps and ht leads made a huge difference to mine, it's worth trying

 

[Traumahawk]

The fan runs pretty loud. I think it will be worth looking into. Because I went through the charging system and am currently getting 14v at idle and 14.5 at 2000 rpms. That is until the motor warms up and the fan kicks in. I did unplug the fan to see if that was the problem and it ran longer, but still stalled out.

What were the volts with it idling and the fan kicked on?

 

[Screwloose]

It sounds like our problems are very similar. It would make sense seeing as how my charging voltages are good, but suddenly drop. I did a bit of searching and decided to get 7mm copper core wire along with the NGK Caps to see if it makes a difference before I get COPS. Also Sean Morley is out of them at the moment.

Sean sounds like the guy to go to for the Vmax parts. I just joined last year during the time i was doing the repairs on mine. I got wrong parts delivered, crap aftermarket parts and so on. I would imagine sean would be fitting the parts he supplies and would know the good stuff from the bad. In my opinion thats 75% battle on these G1’s.

 

[MadHatter16]

Sean sounds like the guy to go to for the Vmax parts. I just joined last year during the time i was doing the repairs on mine. I got wrong parts delivered, crap aftermarket parts and so on. I would imagine sean would be fitting the parts he supplies and would know the good stuff from the bad. In my opinion thats 75% battle on these G1’s.

UPDATE: I couldn't get a hold of any COPS, but I finally got some new caps and leads. I also changed the old sparkplugs out for the E3 replacements and that fixed the problem. I idled in traffic for 15+ minutes after already being at operating temp. The the temp gauge was sitting just below the red without stalling or missing at all.

 

[Fire-medic]

The stock NGK plugs are in my opinion a better choice than E3's which cost more.