Ace 100 Spark Plug

[megawat]

Am using NGK B8HS with stock compression and carb, plug has nice color. Any recommendations on better plug?

[Dale]

I am going to say that you are using the wrong plug. The B8HS is too long for the Ace 100. The correct plug is an NGK B8S. I think you will find that the B8HS has a 1/2" reach while the B8S is 3/8".
Dale

[megawat]

That's interesting. Have used the B8S which is s bit shorter and it runs ok but it has a lot more punch with the B8HS which is hotter.

[racerclam]

Both are the same heat range which is the 8 . Settle this by taking the head off and look at the plug depth in the chamber . What you dont want is exposed threads . The shorter plug may leave a thread or two of the head exposed , that can lead to a hot spot to cause the little guy with the hammer to go ping ping on the inside. I forget which way it goes but the difference between the HS and the S plug was the extended tip verses the standard tip. I used to run the B8HCS Or B9HCS . The C designated competition design , it had a shorter ground electrode and chamfered inner area where the plug body meets the threads, less prone to detonation. Maybe if I think of it I will take a picture of one and post it. That plug hasnt been available for a looong time though.

Rich

[Dale]

Rich is correct in that they are both the same as far as heat range. The H denotes 1/2" reach while the absence of the H denotes 3/8". Unless you have an aftermarket head or a head from a different model, then the B8S is the correct plug.
Dale

[megawat]

Thanks guys, guess I need to pull the head and have a look. Head has decompressor so may be aftermarket but head looks stock and was thinking extra plug hole was done at a machine shop.

[Bruce Young]

Hello Hodaka World, Be careful, as suggested before I too think pulling the head for inspection to find out what the head looks like inside. I would be willing to bet this machine was used either short racing or trail riding. In the old days an Compression release was not unusual on a two stroke machine, no matter what head was used or modified. You need to determine the clearance distant from the plug to the top of piston and maybe even try to determine deck height as well. Double check to determine if the head was cut down. Now back to the plugs, as mentioned before the wrong length plug could cause lots of issues and a big mess as well. First for reference as to what those number and letters on the NGK plug mean go to their web site, NGKsparkplugs.com you will find a chart there that explains all this info and what the length is and what the proper heat range should be. Take a look. It will take a lot of the guess work out of the numbers. Good advice from all, but again be careful what length and heat range of plug is used and what the machine is being used for. Good luck and happy riding. Bruce Young Hodakaparts.com IDAHO

[F150Motocrosser]

My Ace100B also came with a compression release in the head.. I was under the impression that it's a Webco high compression head, as it appears to look identical to one, though I don't see a WEBCO stamping near the plug holes as I've seen in photos.. Assumed it was due to lack of room. Wishful thinking perhaps..

Bruce - So you're saying that adding a compression release it was a pretty common "trick mod" back then?? If so then that really has me second guessing if it's a Webco head or not.. I suppose I'll have to wait and see once I tear into the top end and check and perform the due diligence that you outlined above.

Oh, and I should probably mention that the bike came with a B8S plug, which now sounds like another red flag for my "WEBCO" (using heavy air quotes around that word now)

[RichardMott]

I have a Webco head on my Ace motor. It takes a B8ES. Longer reach. Has been fine since 1974 with that type plug. Has a compression release hole, but I just have it plugged with an old spark plug. See photo.

[F150Motocrosser]

Thanks Richard, I came across your (sweet!) bike today; no bottom cooling fins on mine, so the verdict is in; I do not have a Webco head (insert sad trombone 'wah, wah, wahhh' here).

[MTRob]

Just for fun went on Ebay and found alot of B8HCS NGK plugs. Check it out
MTRob

[sparkyj]

what should the plug gap be?
Oops looked it up. .024