my tecumseh vtwin again-second issue -ignition

[38racing]

It's tvt691 (or ov691) on the zt50 I recovered from fire damage. I actually didn't get it out this year until last week. Cut for about 15 minutes and engine died. end result was the exhaust rocker on left side came loose. I've cut with it ok for about 30 minutes and parked it. Today I got it out again and I had engine misfire that I traced to right side. Initially it would not run on right at all. I did a quick compression and it was good at 120. If you'll recall way back I had issue with brand new NGK br6es which is the equivalent to spec champion rn4c. At one point I had it running on epower e-18, the equivalent for rn4c. For reasons relate dto other engines I ended up with epower on left and ngk on right. Now my testing has had 2 different ngk in right and 2 epowers (including one from left) . Best I can get is it will run on both but shorting left side the right side runs but badly. Severe surging and may still stop.I have another new br6es to try tomorrow. One observation is with the inline spark tester. When I ground it out the test light brightens. I'm thinking that's normal as the path no longer has the resistance of the plug. Assuming it's ignition and not carburetion (remember it has twin carbs) I could swap coils. Prior to doing that I'd like to try a non resistor plug but I don't have a B6ES or equivalent. I do have a projected tip BP6ES . Is that ok to use for a quick test?

[KE4AVB]

Prior to doing that I'd like to try a non resistor plug but I don't have a B6ES or equivalent. I do have a projected tip BP6ES . Is that ok to use for a quick test?

If they are the same as the ones I got which are BPR6ES and the BKR6ES which are the same plug except except one has 13/16 hex and other has a 5/8 hex. And I do use the BKR6ES in place of the BPR6ES. IN your I don't think you will find difference the actually tip length.

Anyways both plugs should the same brand and number.

[38racing]

Haven't worked on it yet but was in shed looking for coil from donor engine. I don't know model of original, but donor is vtx691. When I look up coil 37395 I get it fitting all the tvt691,ov691, and vtx691 and nothing else.
Then I get an ad like this
https://www.ebay.ca/itm/37395-Ignition- ... 4158364098

where it shows different part numbers and engines in description versus the title.
In one ad, if I can relocate it, it clearly states that if original coil doesn't have the 3 notches then don't buy the 3 notches one. So the kicker is I just located the fire damaged coil and it has no notches. I have a single cylinder 16 HP OHV that appears to have the same no notches coil as the fire damaged one. Problem is that I should have an undamageded coil sitting loose either from the zt engine or the donor but can't find it yet and I can't recall if I used both coils from the donor or just one. Be interesting when I pull covers to see what's on it. Meanwhile I have yard cleanup work to get done.

[38racing]

Well after trying another new br6es in right it still wouldn't run. So I swapped the coils and disconnected kill wires from both and no change. So it appears it's not a coil issue. Puzzling still is the ebay seller of 37395 (ipl part number) insists these vtwin oem coils should have had 3 grooves in edge of laminate. I have 3 coils of the 4 on my engines and they're all the same with no such grooves.

[38racing]

I should correct that seller was Amazon. His measurements don't match mine. I looked up 37395 on both Jack's and repair clinic. Both look just like mine so I don't know what these aftermarkets with grooves claiming to be 37395 are.

[38racing]

S not being ignition compression/valve clearance I went to carb. As per last year I was going to start by switching the carbs side to side. But when I took bad one off first I decided to open it. Carb side (output) of main jet looked ok but before before blasting with carb cleaner I looked at input end which has tube for spring mount to tension it. What I saw was a nice piece of crud sitting there. Cleaned it out and its running on both cylinders again.