spark plug question?

[Eddie]

Hi just to update, I replaced the water pump in my 74 gt750, and so far no leaks!!!!!!!! I have rode it about 4 times and dry as a bone!!! now that I said that watch it leak , so my question is what spark plug do you guys run or recommend? the book calls for a b6es I had a b7es(ngk) in it before and it seemed almost oil fouled, but that was whne my carbs were not set right (float level) now the carbs float level is right and they are in sync, so i put B 6 ES in it and the color seems ok but it looks kinda orange? so Im just wondering if the 6 is to hot? maybe I should go back to the 7? I noticed in the book the only gt750 that calls for a 6 is the 74 (L model) and the others have a colder plug , if I remember the heat range on ngk gets hotter with the smaller number right? or am i backwards? what plug do you guys run in the 74 model gt750?

[pearljam724]

The manual suggest running a B6ES for your 74. Being mine is a 76 it calls for B8ES. Both my 75 550 and 76 750 use the same B8ES. Quite a few guys recommend on here a fine wire plug that is a B8EGV. I tried it recently on my 550 and I like how cold starts and warm up are improved by them. But, being yours requires a B6ES, you might want to check into the possibilities of a B6EGV make. If your plugs are whitish orange with little to no oil residue as you say, they are over heated due to a lean running condition. May be your jets, carb boot leaking, crank seals. What ever is causing it. It's running too lean. Plugs are hot. Could also be an ignition issue with the timing being incorrectly set. How old are your boots, do you have original exhaust, how is the bike running ? Hard starts or hanging throttle are both caused by a running lean condition.

[tz375]

I run B9EIX and they work like a charm but I would not recommend such a cold plug in normal bike. I tend to play safe and to me a wet plug is an annoyance but a melted piston is a complete and avoidable PIA - so I tend to go colder than the bike needs just to be safe when I cane it mercilessly.

In your case I'd examine the side strap (electrode) first and see if it looks like the plug is running hot, cold or just right. Any signs of overheating on teh side electrode and I'd slip in a set of B8EV or EG or EGV fine wire to make the most of the marginal ignition system.

Orange is not a normal fuel color and most likely is residue from the oil.

Are you using street gas or some exotic brew? That would make a difference to plug color as well as to jetting.

Can you post a clear picture of the plug tip showing the side and center electrodes?

[pearljam724]

Richard, thanks for recommending the fine wire plugs. I'm now a fan of them.

[Eddie]

The exhaust is the original, no changes, the boots are also the original but they seem to be ok, but then again i wouldnt really know since I have never held a new set, also the bike starts right up no probs and it idles perfect, but i have noticed that after a good ride it takes a while for the idle to drop so maybe it is the boots? i will post a pic, i would rather run a cold plug myself dont want huge probs when i just got it running really good....

[Eddie]

I will take the plugs out to take some pics for you guys, also Im running regular gas, but this last time I put plus which is like 87 oct? I think ? or 86? also Im going to put the B 7 ES in and I just ordered some carb boots from flea bay , crap their expensive!!! I will run the bike with the B7ES while waiting for the boots and keep checking the color, I really dont think its the boots I had hell getting them on the last time but you never know i just dont want to screw it up since its running good right now! thanks for the info and as soon as i can I will post some pics.. also the gas is street gas, and the jetting is stock, everything is stock except I have pods for filters right now, I have the original aircleaner box but I have not put it on , I need the air filter for it, also I like the pods because its easier to work on when taking carbs off, and I am running bellray SI-7 2 stroke oil if that makes any difference..

[Eddie]

ok heres one of the plugs, it actually doesnt look that bad in the pic, but the other one did, my phone sucks for pics, my plugs are either just right or on the verge of being hot. I had taken her for a 30 mile ride and at one time I was hitting 90mph , oopps, then I did the speed limit home and i checked plugs and thats when they looked bad., but it might just be the high speed that did it. I was wondering if anybody has a elevation chart for the jet sizes? I have factory jetting and where I live Im at 3,800 feet., so im sure the jetting needs tweeking, at one time the plugs were oil fouled then I messed with the needle jet, and it looked ok but then that was at low speeds, and after that I realized I had the wrong plug, I had B 7 ES and the booked called for B 6 ES, when I changed to the 6 it was no longer oil fouled but now almost to lean I think, but the pic doesnt look bad though? maybe I should just go back to the B 7 ES and see before I mess with jetting? it has 110 on left and right and 107 in the middle I believe..

[pearljam724]

I agree, it the color I'm seeing is accurate to real life. They seem to be a little on the lean side. But, not bad. I'd say they are from using the pods with stock jetting. You may want to take a step or two bigger on the main jets. Regardless, of your boots leaking or not. If they are originals they would have to be hard. A seller on Ebay has an aftermarket set for $40. Which I refer, as I have purchased them. Just be sure to keep your original clamps as the ones he supplies are supposedly junk. But, I didn't have that problem. An easy test for the boots, is to spray either around the ends of the boots when it is idling. If the engine picks up idle as you spray the boots. There is an air leak.

[Eddie]

Ok one more question, I was looking at jet sizes and I'm just wondering, is it the large round Main jets or the small round main jets? Im not sure. The stock jets are 110 110 and 107 and on the next size up it's either 112 or 115 depending on large or small, and from 107 it goes to like 110 or 115 , I think that's a big step up, but not sure just don't want to go to big....

[pearljam724]

I can't remember small or large round. I believe its small, but double check that. Once you find that out, I'd suggest buying both the 112 and 115 as they are pretty cheap if you buy them from a good source. But, judging by the slightly lean condition of your pics. 112's should get you where you want to be. But, buy both as they are cheap and you can bump it up once more if need be as a result of having them both. Most sellers will combine shipping also.

[Craig380]

Another 10 cents worth here

From the pics, the colouring of the insulator, electrode and outer ring isn't too bad at all, looks like the jetting is pretty close.

However I would recommend going a step cooler on the plugs and fitting B7s. The reason I say this is that the colouring / clean spot on the ground strap of the plug is a little too long for my liking.

If you were just commuting around town and riding gently at speed limits everywhere, the B6s look like they would be fine, but if you're working the engine harder they look a shade too hot to me.

As noted earlier in the thread, Iridium plugs (NGK EIX) work great in old strokers -- just gap them to 24 thou / 0.7mm, fit and forget. They never need regapping, never foul. Sure, they're more expensive than standard NGKs, but you can get them cheap online. If you do fit EIXs, you will need to replace the caps with non-resistor types, as the plugs have a 5K resistor built in.

Good luck, you're nearly there and summer's coming

[Eddie]

thank you all for the help!, I will need to figure out if they are big or small round jets 1st, also I have had these plugs in the bike for a while now so i would think they should be a little darker by now, once i replace the jets then i need to mess with the needle jet so its going to take some time, i just hope i dont get it to far off and get oil fouled crappy running,

[pearljam724]

They haven't gotten darker because of the lean condition. They are burning off any oil residue. The jets will correct it. When you pry into the carbs, double check the float levels again. Until then, try a colder plug also suggested by others. Slightly tacky oil residue is what you want. Just not too wet, that's when you have reached the too rich side. Its safer to be slightly rich, than lean. Your plugs show light tacky residue on the threads, but the center electrode is showing otherwise because it's being burnt off at that point. That's how you know it's not very far off. But, it is. You can't run an aftermarket air filter with stock jetting. It's sucking in more air, than fuel. The air/fuel ratio is off a little. That's all. You'll have to tinker with the jetting to get it right. No brand pods have the same induction rate. This is why you have to tinker with the jetting. Until you hit the correct spot. It's a guessing game with pods, not knowing how much or little they induce air. Some brands are made of different screening elements and sizes compared to others. Some suck so little air stock jetting will get you close. Some suck so much, the main jets need to be raised.