T500 K left cylinder cold start issue

[Ifrew]

I've been tuning my 73 T500 and I've got to the point where it's pulling well through the range to WOT and idles well. The bikes carbs are from a 72 with the float bowls from a vented 73 and it has K&N Pod air filters. Currently running with #35 pilot, p4-5fp17-5 and 117.5 main. It took many iterations to get to this point.

Issue I have is that from cold, when I use the "choke", the bike only starts on the right cylinder until I turn off the "choke" then the left cylinder fires up.

I thought it was due to the large pilot jet somi dropped.it back to #30 with same issue. Running with the #30 makes the bike judder when I close off the throttle but when I move it back up to #35 the judder disappears. I assumeed the judder was due to the smaller pilot not delivering enough fuel due to the larger k&N pods.

So now I'm a bit stumped as to why only the left cylinder has an issue. New battery is fully charged.

Any idea folks?

Cheers
Iain

[Ifrew]

Thought I'd swap the plugs to see if there was any difference. Started first time from cold with choke on both cylinders. Strange..must be a difference in the coil output and the plug/cap resistance..I'll check that next. Turns out one plug cap resistance is 5kohms the left cylinder and the right is 9kohms...ill order up new caps and I'll check the coil resistance.

[karl pa]

Good catch.
I use non resister caps and plugs for full spark. Also beware of counterfeit NGK plugs, I buy mine from a reputable dealer.

[jabcb]

I use either non-resistor caps + resistor plugs, or resistor caps + non-resistor plugs. Fine wire plugs also helps.

[Craig380]

If you can get an Iridium equivalent for the stock plugs, I would recommend fitting those.

On my old 380 I experimented quite a bit with various plug types - standard, gold-palladium, platinum and iridium. Using the iridiums with standard gaps (0.7mm) and non-resistor NGK caps was easily the best: the plugs never fouled and never needed re-gapping, literally fit and forget. The bike was running the factory points ignition and coils.