How to Check Coil - Rear cylinder cold

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Peeb
Posts: 18
Joined: Tue Apr 11, 2017 6:07 am

How to Check Coil - Rear cylinder cold

Post by Peeb »

Hello,
INTRODUCTION
I bought a low miles 1998 VTR 1000 a two years ago. It ran poorly and thanks to advice from this forum it is perfect. I did the CCT Stopper Mod, replaced the voltage Regulator, TPS adjustment, new fuel petcock diaphragm, new fuel hoses, new fluids, removed the Pair system, rebuilt the forks, rebuilt clutch and slave, new tires, new chain & sprockets, went from 45 to 48 pilot jets. The effects are fantastic, great steady state operations, never stalls, and none of the irritating tail pipe explosions when decelerating. The results are a low mile time machine. She does smell a little rich when I ride behind my son on the VTR.

PROBLEM
Recently, the rear cylinder cuts out occasionally and then completely after about 15 min of run time. After running perfectly through warm up, it happens every ride. The rear header pipe is just warm while the front is spit hiss hot. After a 25 min cool down all is back to normal for another 10 min operation. My first thought was the rear plug fouled because we went to rich. The plug is a bit dark but fires well when grounded to the frame. I can't get the tank off fast enough to reproduce the problem while hot. I replaced the plugs anyway with no improvement. For want of the peak voltage adapter 07HGJ-0020100 and inspection adapter 07VMJ-0020100 I'm unable to do the Ignition System inspection found on page 17-4 and 17-5 of the official Honda Service Manual. I do have a good volt meter. On a bench, the resistance between the green and black wire is .6 Ohm. The resistance between the green or black wire and the spark plug connection is 18,000 Ohm.

QUESTIONS:
1. How do I bench test the coil? On older automotive single coil systems, there is a primary and secondary resistance measurement. I see no resistance numbers or methods for doing this bench test in the Honda manual.

2. Is there a need to look at the Ignition Pulse Generator? My assumption is a defective pulse generator effects both cylinders equally.

3. Have any of you experienced a failed coil and did it fail after warm up?

4. Can the tests be done without the Honda Tool?

5. Anyone know where to buy the Honda tool? It looks like a wire harness in the sketch

4. Other ideas?

My local dealer won't touch a bike older than 2004. This is a 21,000 mile super super bike and I'd hate to loose it to something stupid. If I missed something in the Workshop Topics I'm sorry - just send me to the right link.

Thanks, Peeb
Seattle Washington USA
tony.mon
Posts: 15943
Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: How to Check Coil - Rear cylinder cold

Post by tony.mon »

One easy way to check is to swap the front and rear coils and see if the problem moves, too.

They won't fit exactly, but just bolt them to something solid temporarily so the the lead length still reaches the spark plug, and if you need to, run short extension lead on the one that won't quite reach, on the feed side.

TBH for the amount of money, why not just buy a 2nd hand rear coil and fit that- it's a quick, easy, and cheap fix. If it doesn't fix it, just sell the coil on and get your money back.

The other possibility is the plug cap; again, just switch them both over. Maybe try this before swapping the coils, as it's easier, and you have to take it apart less...
It's not falling off, it's an upgrade opportunity.
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E.Marquez
Posts: 635
Joined: Wed May 30, 2012 1:27 pm

Re: How to Check Coil - Rear cylinder cold

Post by E.Marquez »

So two thoughts..
One is, junk the big fat OEM coils, old spark plug wires and caps, and convert to Coil on Cap.
Second; if you have a multi meter you can do a few basic checks on the OEM coil.
https://www.howtomotorcyclerepair.com/testcoils/
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Commando77
Posts: 199
Joined: Sun Oct 08, 2017 10:35 pm
Location: Fleet, Hampshire

Re: How to Check Coil - Rear cylinder cold

Post by Commando77 »

You said 6ohm between Lt leads. When I thought I had a coil issue recently mine measured 1.2ohm and they are both fine. 6 seems high for this kind of electronic ignition. I'm surprised its not part of the spec but I guess its a bit more sophisticated than electronic ignition I'm used to.
tony.mon
Posts: 15943
Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: How to Check Coil - Rear cylinder cold

Post by tony.mon »

If I recall correctly Storm coils output higher voltage than most other coils.
Haynes will have the specs.
It's not falling off, it's an upgrade opportunity.
Peeb
Posts: 18
Joined: Tue Apr 11, 2017 6:07 am

Re: How to Check Coil - Rear cylinder cold

Post by Peeb »

OK, I bought a new coil. The Primary Resistance is the same. The Secondary resistance is different between the new coil and the old one. The new Coil is installed and the bike runs fine in the garage but we have temperatures below freezing along with snow and ice on the roads so it may be a couple weeks before we can run it long enough to see if the back cylinder drops out again.
datomo
Posts: 5
Joined: Wed Jun 24, 2020 9:04 am

Re: How to Check Coil - Rear cylinder cold

Post by datomo »

gday how did u go with the coil? mine is doing exactly the same thing ruins fine until out on the road, did the new coil end up fixing the problem ?
FlyingElk
Posts: 4
Joined: Mon Mar 21, 2011 5:07 pm

Re: How to Check Coil - Rear cylinder cold

Post by FlyingElk »

Sorry to bump an old thread. Keen to find out if the coils could be the culprit for my bumpy acceleration/acceleration delay/backfiring when warm. Sounds similar to what has been described here. Did replacing the coils solve your issues?

Cheers!
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