Hot Spark Plug....

Little tricks and some things you shouldn't do for your L Series Suzuki

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Jimny
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Hot Spark Plug....

Post by Jimny » Sat Apr 02, 2005 4:38 pm

This is why you do NOT use the 'HOT' Spark Plug in a LJ!
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Post by Smuz » Sat Apr 02, 2005 5:03 pm

I got one that looks JUST like that. From a set of hot (long reach) plugs, too.
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Post by Jimny » Sat Apr 02, 2005 6:23 pm

long reach
I guess they wanted to have a hot spark AND get the combustion right at the top of the piston. Wow just imagine the Power! :wink: :wink:
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Post by russmehl » Sun Apr 03, 2005 6:58 am

So you get tired of cleaning the plugs, and put in hotter and hotter plugs.
Soon you are not cleaning plugs, but scraping piston bits out of the crankcase and off the reed valves. What a tradeoff!

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Post by lil_zuk » Fri Aug 05, 2005 3:14 pm

Yea, along with running hot plugs highway driving can take its toll on the little 2 strokes.
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Post by lj20Colorado » Wed Oct 19, 2005 9:32 am

what kind of power increase would a person get with the hotter spark plugs in there lj20 vs regular plugs. is there a hotter spark plug that wont hit the cylinder. just asking for off road use only not on highway use thanks.
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Post by stevec » Wed Oct 19, 2005 10:09 am

Most spark plugs come in "heat ranges". For example, a stock spark plug for an LJ20 is BP6HS. BP7HS is the exact same size, but burns cooler. (for most brands, lower number means hotter). If you went to BP5HS (assuming it exists), it would look just like the stock plugs, but would burn hotter. In the short term, you would have a little more power, but the pistons aren't designed to withstand that heat, and it eventually burns a hole in the piston. Jimny's picture is a good example of this; his plugs were not the "long reach" style. Offroad driving vs. highway driving won't make a difference here, because the plug is always burning too hot. What lil_zuk is saying is that, even with the proper plugs, extended highway driving can generate too much heat, (due to running high rpm's for a long time) and eventually burn up the pistons.

Short answer: Stay with the stock plugs!
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Post by lj20Colorado » Wed Oct 19, 2005 10:14 am

oh ok thanks steve.
what are the best spark plugs to use ?
thanks.
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Post by stevec » Wed Oct 19, 2005 10:39 am

I prefer NGK, but you can also use ND. I wouldn't recommend any other brand.
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Post by p08man » Sat Feb 09, 2008 9:32 am

Has anyone in the group tried using spark plug extenders to reduce tendency to foul? Ive used them on other vehicles with favorable results but never on my LJ's.
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Re:

Post by deimos_jr » Sat May 17, 2008 12:05 pm

stevec wrote:I prefer NGK, but you can also use ND. I wouldn't recommend any other brand.
I use NGKs in my dirt bike too. Its four stroke, but I still notice a difference between off brand plugs and NGKs. I think thats the recomended spark plug for all japanize vehicals because we use them in the samurai too.

Hey Jimny, what sort of noises did the engine make when that piston blew up? Did it just die?
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Re: Hot Spark Plug....

Post by Smuz » Sat May 17, 2008 6:01 pm

Mine made no unusual noises of any kind. It just died.
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Re: Hot Spark Plug....

Post by deimos_jr » Sat May 17, 2008 6:37 pm

Well thats good. I wouldn't want to run it with bits and peices clankin around in there.
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Re: Hot Spark Plug....

Post by Idahopaul » Tue May 20, 2008 5:38 pm

ya they do so much damage in the first 30 seconds its not imaginable what would happen if it was ran any longer! I only have experience with a few bikes that did this. they do this when too lean a air fuel mixture too, like when the crank seals are getting weak. thats the problem I had with the bikes.
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Re:

Post by Jimny » Wed May 21, 2008 5:51 pm

p08man wrote:Has anyone in the group tried using spark plug extenders to reduce tendency to foul? Ive used them on other vehicles with favorable results but never on my LJ's.
Never have tried it, I usually have no problems with my plugs fowling.

I don't see why they wouldn't work unless they are too long and it will be hard to get the plug wires on.


JR: I only had one LJ make noise when it died, it was my first LJ10 and it went CLINK! and then I had no power, it bronk a ring (or two) and it just did not want to run.
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Re: Hot Spark Plug....

Post by tweeder » Wed May 21, 2008 6:03 pm

i had one make a noise when it died.....sounded like a friggin 10ga shottie. then, couple miles later, the gasket gave out and it quit runnin...
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Re: Hot Spark Plug....

Post by Jimny » Thu May 22, 2008 3:35 am

Just so you know JR, Tweeder's failure wasn't due to a Hot Spark plug. :wink:
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Re: Hot Spark Plug....

Post by tweeder » Thu May 22, 2008 6:54 am

ya, i was just slow on the whoa! :shock: if i'da got the brakes pumped up quicker or had stepped on the clutch (now THAT woulda been a wild ride!!!) Jimny wouldn't have that engine in his shop.
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Re: Hot Spark Plug....

Post by russmehl » Thu May 22, 2008 7:42 am

It's funny how easily mine will run backwards, don't know if it has anything to do with the home made electronic ignition. I was turning around in close quarters and bumped up onto a pallet of bricks. Shoved in the clutch as it was rolling back and stalling. Put it into reverse and let up the clutch. Right back into the bricks! Shut off and restarted...
Can't imagine the oil pump works well in reverse... :ohno:
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Re: Hot Spark Plug....

Post by tweeder » Thu May 22, 2008 7:53 am

logically, there SHOULDN'T be a problem with a 2-stroke running bass-ackward except the timing being WAY retarded..... but that one sure didn't like it! :shock:
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Re: Hot Spark Plug....

Post by stevec » Thu May 22, 2008 9:13 am

When I put the Pertronix ignition in my RHD, the timing was way off, and it ran backwards. A little grumblw when it first cranked over, but then it ran fine. I didn't know it was turning backwards until I put it in first, let the clutch out, and started backing up! Took me a minute to figure out what happened...
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Re: Hot Spark Plug....

Post by Smuz » Thu May 22, 2008 10:32 am

In the early 70's, Mercury made some outboards that didn't have a reverse gear. When you put it in neutral it died. For reverse, they retarded the timing a lot and it would crank, start, and run backwards. These were around 70hp motors and they had a nickname among boat people: they called 'em "dockbusters".

Ya better keep 'em tuned up so they start easy.
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Re: Hot Spark Plug....

Post by tweeder » Thu May 22, 2008 10:52 am

dockbusters, eh? must be a term of endearment :))):
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Re: Hot Spark Plug....

Post by Suzy » Thu May 22, 2008 7:11 pm

Some older large marine diesels are like that too. I worked on a tugboat built in the very early 1900's, it's original steam engine had been replaced with a diesel just after the war. To select reverse you shut it down, flipped a lever and then restarted the engine in reverse. This worked great till the air compressor failed, it was air start and the compressor parts were no longer available so the owner of the vessel replaced the compressor with a new but much smaller unit. Worked fine most of the time, different story though going to the hydroplane races on Lake Union, there is a set of locks to get through to get into the Lake and lots of small craft around. Maneuvering in the locks required a lot of stops and starts, more than what the compressor could deal with. It is a good thing no little fellars got in the way and that they built the lock gates and tugs bow as strong as they did. I can't remember what she weighed in at but at 100' she had to be heavy. The engine was probably 10-12' tall and 20' long.

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Re: Hot Spark Plug....

Post by redsnodog » Thu May 22, 2008 10:16 pm

As a "FYI" from our experiences with sleds and dirt bikes 2 strokes have no problem running backwards.For at least 5 or 6 years now Bombardier has offered an "electronic" reverse for there sleds which only require a push of a button while idling.The engine slows right down as though it was dying and lights right back up within a half second or so and runs backwards.Instant reverse!The ignition module plays with the timing to facilitate this.
A few manufacturers have offered extended nose core spark plugs as anti fouling plugs and as long as they are used with the same heat range are not usually an issue as far as burndowns are concerned.Most two strokes burn up because of lean fuel conditions due to failed base gaskets, crank seals,etc. or oiling trouble.[I'm sure this isn't news to anyone here,but thanks for letting me babble]Having been in the automotive parts/equipment business for 20+ years we were asked to sit in on lots of product seminars.
Spark plug mfgrs were telling us that an ideal plug tip temp was about 1200 degrees F.Since different engine designs generated different degrees of heat by comp. ratios,head design,squish etc the plug had to either retain or shed heat a a set rate to maintain this temp.The longer the center insulator the longer the heat path and the "hotter" the plug was as the heat had a longer path to take to shed its heat throught the plugs threaded area and into the cyl. head.
Playing with heat ranges would mean your plugs tip temp would be more or less than the designed 1200 F.To hot a heat range would make the temps get to a point where preignition/detoation would occur and burn away the piston top like in the picture.Too cold and the plug will foul.Sticking with an OEM plug is a good idea we were told because the cross referenced alernate mfg plug would not likely be the exact heat range match and would operate somewhat higher or lower than the ideal 1200 degree mark.How hard we work a given engine will affect combustion heat and therefore the plug selection also!Adding copper to the center electrodes as they have done lately widens the operating window to better maintain the ideal tip temps.
Now there is a pile more useless info for us gearheads,thanks for the space!!
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