Witt or coil?

N

neilmc

Junior member
Location
Tasmania
I have a weird problem, bike is fine running for about an hour then progressively cuts out as it heats up. This is obviously ignition, I have Witt (bought '92) and associated coils. Has anyone had a similar problem? My instinct would be coils, but the Witt is a few years old. Must be something heating up over a period. Anyones input welcome! Witts must be pricey these days, were ?400 odd in 92, so may replace one or both coils first up.
Apart from being left on the side of the road, runs fine with newly synched carbs with the Carbtune!
Neil Mc
 
Yes, had a similar problem with the 3CL in 2000, got worse over time. Replaced the twin coil and the problem went away. If you have access to some second hand coils I'd try that first.

HTH
Gerald
 
Classic case of old coils past their used dates.
Coils are,well,coils of wire enapsulated in resin.
If the wire is cracked by age,when the resin heats up and expands,a gap in the wire appears.
Hence no spark.
Let them cool for a few hours-hey presto---spark.
 
If the twin coil on a 180 degree engine claps out you have f... all performance and it will feel like the ignition cuts out. Easily diagnosed with used coils to isolate problem and resolve the issue at a reasonable cost, before investing in a new ignition of questionable quality!
 
this is whats happenened on my  180 coil thread ,double coil failed, i  thought, got home on centre just,however it goes deeper that as Tek coil doesn t spark either  :(
 
Thanks for all the feedback/comments etc, gives me some confirmation.
I tended to think the Witt wouldn't be the problem, else it would happen when cold as well. My suspicions were towards the double coil, which seems to be a contender to fail! After thinking about it, have had the same problem with 4 wheeled vehicles in the dim distant past. Anyone know what type of coils Witt used? They were obviously off a 4 cylinder Japanese bike of some sort, one of my HT leads still has a number 4 on it!

Cheers,

Neil Mc
 
Thats a good idea, they go through that connector under the seat, potential for problems. I think the coil is probably cactus tho.

Neil Mc
 
G'day Neil

I had similar symptoms on my Jota a while back. It was actually a fault in the Witt DMC1. Uwe Witt sent me a voltage limiter which fixed it for a while, but it was never 100% reliable. I replaced the whole lot with a Redax alternator/pickup assembly and Ignitech ignition a few months ago.

Anyway, check your coils first. I have a spare set of single and double coils if you want to try them (off a Honda). If that fixes it, good. If not, I also have a spare DMC2 (brand new), series 1 pickup plate & alternator assembly in working order.

I sent you a PM with my contact details.

Cam
 
Had a similar problem a few weeks ago, 3CL with a DMC2 and new coils installed around 7000km ago. She ran fine for the first 100km or so, then started missing, backfiring and cutting out. Just got worse n worse. A half hour rest, and was OK for a bit. Was thinking bad coil, having checked the wiring. Eventually found an almost new NGK resistor plug cap to be open circuit. The other 2 plug caps measured 5K ohms, as expected. Replaced all 3 caps. Now OK, but need to do a few thousand km to be certain.
Easy to test. Worth a try?
Lex.
 
Lex, it tends to happen on at least 2 cylinders, (possibly even 3?) so it wouldn't be just one cap. After talking to Cam will try a secondhand coil and go from there. If all 3 cyl are cutting out it could be the Witt unit itself. The hard part is duplicating the problem as it normally happens at the worst possible time like on a no stopping road or uphill! Had a Lucas ignition on a Triumph twin crap out while touring NZ in the 80's, normal story, middle of nowhere pissing with rain, ignition craps out! Went Boyer after that, but you had to time it at 5000rpm! Twin grooves in the concrete from the mainstand. 
Maybe I can find a good short test circuit that includes a pub.

Neil Mc 
 
Hi Neil,
the way she was missing n farting, I also thought it was a bad coil. Couldnt tell whether it was a single or double coil. Loss of power, one cylinder or two, then after a minute or so, would cut out. I suspect the DMC2 uses coil firing pulses as part of the equation to calculate advance, so the poor bugger was getting totally confused, then shutting down. To confuse the issue further, the longer I was stopped, the longer it took to play up once I was going again. At one point, removed throw over panniers so I could lift tank to get at the coils. Removed em, checked wiring continuity, found a bit of water around/on the coils. This took 40-50 minutes before I was mobile again. Ran OK for a 100km after this, then played up. Stopped for a fag, then got home OK, 40km.......

A very quick and easy check. Must say I was surprised that a cap caused the symptoms (bad coil fer sure) I was seeing. Never seen it before quite like this, with 45 years of playing with engines.
Lex.
 
Lex,

That's interesting, it does have similarities. My Witt is pretty old, '92 LC2.1. May be tougher than the later ones, or it may be buggered! My 1st symptom was pre-ignition at highway speed (100k), backed it off and got slower but got home. Then yesterday just cut out slowly, wouldn't support the throttle opening, pre-ignition, back off then 1 or 2 cut out then all 3 in about 30 secs or so. Wait 10 mins and away again, same thing in about a mile. Will just have to work through it starting at coils, connections etc. Presumably the resistance for the cap is just through the cap from HT to plug.

Cheers,

Neil Mc
 
Hi Neil,
really easy to check. Just need a multimeter, set to read on the 10K or 20K ohms scale, probe in each end of plug cap, having unscrewed the high tension lead. The good ones i've tested read 5,000 ohms, + or -  30 ohms.
The bad one was open circuit. Also saw corosion in the HT lead, but only on the one to the bad cap.
If this sort of shit is not yer cup of tea, send a mail. I should be able to talk you through the process.
Lex
 
Had a similar problem with my Duc. PO told me keep the plug cap off the plug but close enough for spark to jump the gap, dunno why that worked, but turns out there was corrosion where the coil picked up its ground at the frame. A bit of steel wool buffing on the frame solved it for good.
 
No worries, I have a good multi meter (analog), bought to rewire the bike. Must check the earth (ground) as well, just in case corroded/painted.

Cheers,

Neil Mc
 
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