Important: check your plug caps

[Phil_H]

A couple of years ago, I purchased a tidy low mileage '90 vfr 750 which had a misfire/stumble - worse when hot.
I checked & double checked pretty much everything.
Long story short, I discovered it was the plug caps, they had sky high or infinate resistance when it should be 5k ohm
I stripped and cleaned the plug caps internally, they had lots of burnt corrosion. After cleaning, the resistance was 5k ohm
I still have the bike and it has run perfectly ever since and I now make it a service item on any bike I purchase over about 10yrs old.
I then did the same with my nc30, and several other bikes since

Fast forward, I bought a '99 Vara and joined the site for cct info.
While poking around the bike, I unscrewed the rear plug cap - very variable resistance, the front one was infinate.
Both caps cleaned up and now read 5k ohm.

What to do;
Unscrew the cap from the HT lead, the part of the cap that fits onto the plug has a slot, unscrew this with a large flat blade screwdriver & remove, the (5 k ohm ) resistor will fall out too.
Deep in the shaft of the cap is a longish spring, hook it out - they can be stubborn as often they are corrosion welded in place!
Use a sharp long flat bladed screwdriver & scrape the head of the cap, where the spring sits. Scrape thoroughly until it is a nice bright brass colour.
I usually shake the dust out, spray with wd40 or similar to rinse before reassembling (clean the spring up with a dremel/ wire brush or emery).

Test, with a multimeter, if you don't get a nice clean 5k ohm while trying to gently flex the cap, strip & start again!

Before screwing the cap on, snip 10mm or so from the end of the ht lead.

Hopefully this will be of benefit to someone ;)

Phil

sent from my 'phone

[VTRDark]

Good info that

The other option is to get rid of the old coils and leads and fit coil on caps (stick coils). http://www.vtr1000.org/phpBB3/viewtopic ... 31&t=21761

Get rid of the lead in between altogether.

(:-})

[sirch345]

Very interesting Phil, nicely written up as well

Re:- snip 10mm or so from the end of the ht lead
We've come a cross that suggestion on here a few times, although I've never seen the rest mentioned before. It does make sense to me.

Chris.

[Phil_H]

Stripping the plug caps has made a significant difference on 1 bike with running problems & a noticeable difference to a couple of other older bikes that showed no apparent running issues.

I'm expecting to notice a difference with the Vara ;)

Of course, swapping to COP caps or aftermarket replacements are other options, I like the stock caps as they have properly shaped & placed mouldings to keep moisture & crap from the plug recess ;)

Phil

sent from my 'phone