Will a plug change an engine's torque?

Discussion in '2-Stroke Engines' started by Motorbike Wanabe, Dec 24, 2009.

  1. I just changed out the plug that came with my HT Grubee GT5 angle plug engine and it runs great. But, the real low torque (like when you're starting out) seems to be different. Like there is a lot less of it. I also changed the needle setting from the second from the top to the top groove, but I did that before changing the plug and I have driven it some since doing that.

    Just to be sure, I moved the needle back to the 2nd groove and, also went down to the 3rd groove. It 4-stroked pretty constantly on the 3rd groove, ran okay on the 2nd with some 4-stroking and seems to run great on the top groove, except that it just seems down on torque. Once I get going, it runs awesome! Throttle response is great and, it'll go faster than I care to go with it. I'm just wondering if the plug could have something to do with it "seeming" to lose some of that low-end torque as it starts out.

    I've read repeatedly to replace the factory plug with another one so I replaced it with an Autolite 425 like I read on this forum. Like I said, it runs GREAT except that I think it had more grunt just off idle before I did, or something, happened.

    More info: I gapped the plug at .028" and the plugs appear to have the same depth. I've heard of indexing plugs to get the opening of the electrodes pointed in the right direction so they are not shrouded. Maybe that might help? Any info is appreciated.
    Last edited: Dec 24, 2009

  2. give me vtec

    give me vtec Active Member

    yes the spark plug can make a difference. If it isn't gapped correctly you can lose some spark. If you get a better plug you can gain some... There are some that reach a bit longer into the combustion chamber and displace volume, bumping the compressions slightly.

    I dont know exactly what caused the change in performance you are talking about... but it is possible.
  3. Thanks Vtec.

    I just got back from a longer ride where I had the chance to stretch out the engine a little bit. It's really running great and I'm even starting to think that it's not running any different on the low end but it's running so much better on the top end that it SEEMS to be missing something down low. That might sound weird but, the engine is just getting broken in and that might be making the difference. It's got plenty of torque once it's moving and there's a pretty good sized hill near me, I've just not had the chance to get over there yet to see how it's doing. That is the hill that separates the men from the HT boys around here. we'll see!

    The engine was always a little sluggish when I first start riding it for the first time but once it got up to temp (and cleaned out the extra fuel from choking it) it runs great. I'm even thinking that it might just have needed to clean out a little bit with a good long run.