OK On my virago well I am trying to find out how spark plugs affect the starting of the bike.
OK In winter it ran great with the BP6es which is 1 hotter than the BP7es its designed for. With the 7 it ran like crap and I went to the 6 nd it cleared up.
Now I went back to the 7... damn it it was 70 degrees last week and it didn't start when it dropped to 30. When it was 70 it started and ran like a dream of course. Needless to say the heat range comes in when its running. But does it influence starting. Yes I know it will probably be fine with the 6 plugs in it, and next week on it wont hit the 30's here till december... but there is somehting I need to learn here so I am asking.
Cool.
Srinath.

Put a set of splitfires in it and forget about it!

They won't save you any gas or give you any added HP but....
Years of dirt bike racing taught me they start easier and foul less than any other plug.

..............And they make your bike louder. :mrgreen:

Try them and your bike will start(and run) much quicker in any weather. (especially cold) I can ride off on my bike (choke off) in about 1 min. in 32 degree weather.

I'll be putting on my flameproof suit now.... I can already feel the many NGK fans preparing to flame me.
(don't bother if haven't actually tried both kinds in your bike)

Interesting info, BanannaMan!  I'll have to try me some of those Splitfires.

Srinath, is your specific question about the effect of the plugs' heat range on starting the engine?
(You really should use a "?" when you ask a question.  Otherwise folks can't tell.    Just kidding ... sorta.   :mrgreen:  )

Anyway, I'd like to know the answer, too.  "Anyone?  Anyone?"

BTW - Where did those "BP" numbers come from?  This is what the Haynes manual says:For cold climate (below 5 deg C) .... NGK DPR7EA-9 or Nippondenso X22EPR-U9
Standard ............................ NGK DPR8EA-9 or Nippondenso X24EPR-U9
For extended high speed riding ...... NGK DPR9EA-9 or Nippondenso X27EPR-U9

ive had probs with splitfires in my cage, almost melted the stock plug wires? put on a set of accel (cant remember which ones) no probs what gives :dunno:

OK You 2 (not kerry the other 2) aren't any help... I can put in the BP6's and it will be fine. Kerry these are on a Virago 535 not GS. The bike has specs on switching plugs when cold. However I also realized the answer to my own question (Picture tossing and turning in bed here). Heat range refers to the heat the plug reaches when running, and that makes the cleaning of the plug better. Hotter is cleaner, but hotter also will make your plug burn up if not used properly and will make it misfire and in general act up. So with the 7's when I ran it, it didn't clen up enough to make it start in the colder weather... hell might not start in warmer weather either cos I put in a plug that had been cleaned before putting in.
Cool.
Srinath.

Quote from: seshadri_srinathKerry these are on a Virago 535 not GS.

Oops - virago was the 4th word in your original post!  
Sorry about that.

The next time I "sorta" kid you about punctuation you can  :guns:  rib me right back about reading every word before I put my fingers in gear....

PS - I'm glad you figured out the answer

Just for my own curiosity Srinath, how long and what sort of usage was the bike under when it was 70 degrees with the colder plugs?  (I think thats the way it went, I started confusing myself and re-read the OP 4 or 5 times)

~20 mins, no fast or high speed riding... just round the block types. I pulled them out and they were gas fouled... but that was after they failed to start. I also may blame old gas, though its only 2 months old.
Cool.
Srinath.

Too bad they don't make a plug halfway between those heat ranges.

You MIGHT be able to "make" a plug that behaves like was between ranges but it would be a ton of trial and error. A dab of anti-seize compound around the threads of the colder plug might warm it up just enough to be useful year round but anything on the threads generally isn't recommended.