What replacement spark plugs do you use? (chinese 2-stroke)

Discussion in 'Electrical' started by srdavo, May 31, 2007.

  1. srdavo

    srdavo Active Member

    here is the list I compiled a couple years ago.

    NGK B6HS & B5HS
    Champion L86C
    Champion CJ7Y low profile ( I like these)

    Autolite 425
    ND W2OFS_U
    Bosch W9EO

    The plugs in bold print are the ones I have personally and successfully used.
    does anyone use any of these?
    has anyone found more to add to the list?

    I want to confirm my list, but NAPA only carries the 1st three .
    Last edited: Aug 11, 2008

  2. OldPete

    OldPete Guest

    One should not use plugs that place threads inside the combustion chamber for two reasons.

    1- The thread/s can fill with carbon and start damaging fragile aluminum cylinder head threads when removed. It can get so bad the plug threads go into a bind at removal.

    2- With extended heavy load on a hot day the thread that is exposed inside the chamber can glow just enough to induce deadly detonation. This leads directly to a holed piston or a piston seizure. Bad stuff for sure.

    (I have seen a seizure cause by a Heli-coil plug hole repair that was hanging into the chamber by half a thread.)

    Solution? Use an old gasket along with a new one or use a solid copper ring to space the plug out enough. This is the only image I could find on a quick search. Called index washers. They are used to place to open side of the plug gap directly at the incoming air charge when the plug is tightened.


    srdavo, delete this if you wish. :cool:
  3. gone_fishin

    gone_fishin Guest

    my ngk b6hs is exactly the right length on my dax70.

    can anyone confirm any of the other numbers? we wanna make sure the manual is correct.
  4. locoWelder

    locoWelder Guest

    Denso ift-16 Iridium Power !!!!!!!!!!!! 8)
  5. Herrmanator8

    Herrmanator8 Guest


    I have an 80cc bike motor that i bought from kingsmotorbikes and it came all stock and the spark china plug is stock. Is the stock spark plug the right length, id like to know whats the best/highest performance spark plug i can get and it must be the right length because i dont was and engine seizure or any other problems in addition to the ones i already have. so can someone please tell me what i should get plz, and maybe some good advicel.

    Thanks, Jon Herrmann
  6. Guest

    Guest Guest

    NGK B6HS OR B5HS are the best direct replacements.

    I have fitted an Autolite 4093 with no problems, but haven't checked to see if it goes into the cylinder at all.
  7. spark plugs

    I have not messed with these in years, but I can tell you that I remember that not all of the heads are threaded the same depth, and in many cases the orig plug is actually too short,. Mike
  8. OldPete

    OldPete Guest

    Re: spark plugs

    Every home-brew mechanic should have one of these, they can be had in plastic, from Harbor Freight for <<$10. A vernier caliper w/depth gauge.

  9. Guest

    Guest Guest

    ...or take the head off and screw your plug in and see where it ends up.
  10. jol

    jol Guest

    I got a NGK B6HS as spare, but use the one that came with the motor
  11. lotsa_mpg

    lotsa_mpg Guest

    I had the head off of my Chinese 80 today and checked a few different plugs I had in stock to see how they fit.

    This pic shows an NGK BPMR7A (equivalent to a Champion CJ7Y). Notice that it does not reach the bottom of the threads.[​IMG]

    This shot shows the stock plug that came with my engine. It is stamped NHSP LD Z4 071. It nicely reaches the bottom of the threads.[​IMG]

    This one shows a Bosch W150M11S (equivalent to an NGK B6HS). This Bosch plug was discontinued back in about 1979, but I still have a couple hundred new old stock ones sitting on the shelf. It seems to fit the same as the original plug. I'm going to put some of these in all my bikes and see how they work. It's a pretty nice looking plug.[​IMG]

    I noticed that someone had recommended the Champ CJ7Y. I would not use it in my bike because of it being too short....but it's quite possible that not all Chinese heads are of the same thickness as mine, so it might work well on some engines.
    Timbone likes this.
  12. azbill

    azbill Active Member

    nice post dude !
    shows exactly how n why
  13. Guest

    Guest Guest

    Empirical fact finding at it's best! Thanks a million!

    BTW- the middle (original) plug looks like it's being run on the ragged edge of too lean. Or is that the stock un-run color?
  14. lotsa_mpg

    lotsa_mpg Guest

    Glad I could be of help. And yes, Joe....that stock plug is awfully lean. It's from my PK80 that I'm having real probs with (see explanation in Hardly Davidson post in picture gallery). I finally have the bike running to a point where it's half acceptable, but it's still lean and I can't figure out why. I'll likely end up blowing it up.

  15. Chopper

    Chopper Guest

    I just put a Champion L86C in mine this afternoon, seller assured me it's the equivalent of the NGK B6HS.

    It's still raining here so I may be able to do some on road testing tomorrow.

    btw lotsa, excellent post! :)
  16. Herrmanator8

    Herrmanator8 Guest

    the other day i was strollin by the lawnmower section in walmart and theres the assortment of air filters and spark plugs, till one plug cought my eye! its called the DIAMONDFIRE E3 spark plug. i bought it for $5.88.

    i havent tried it yet but the package claims that it reduces gas waste because there is more spark, in which burning everything, thereby improving mileage.
    ill get back on everyone on the results.

  17. lotsa_mpg

    lotsa_mpg Guest

    I've never heard of a Diamondfire plug before and would be interested in finding out how it works. Personally, I think lots of plugs are advertised to be the greatest thing since sliced bread (I'd rather buy an unsliced loaf myself). The people who dream up the marketing schemes must have been snake oil salesmen in prior lives. I've sold snowmobiles for many years and it's incredible how many owners swear by a particular brand and call others junk. I don't think that any one brand is inherently better than another. But, there are situations where one makers plug seems to work better in a specific engine than any other brand. I do not believe this is because of any superior technology, but rather because of a more accurate heat range for the given engine. What I'm trying to say is that I don't think the cross reference charts are 100% accurate. For instance, an NGK BR8Es is supposed to be equivalent in heat range to a Champion RN3C, but is it really? I sorta doubt it. It would likely be more like a RN3.1C or an RN3.2C (if there were such a plug, and there isn't). So, I believe this is why some people claim that Brand X is the only one to use....it worked great in their engine, but on the next engine, another brand may work out better. A few years ago, there was something called a Splitfire plug that was all the rage in the snowmobile magazines (the ads claimed similar benefits to your Diamondfires). Everybody that walked in the door asked if I carried them. I'd never heard of them before, but I quickly ordered a bunch. Wow, with a fresh set of Splitfires, most snowmobiles seemed to gain performance in a big way for the first mile.....unfortunately, the Polaris sleds I sold ate the Splitfires up very quickly (they usually wet fouled within a few short miles). My distributer didn't seem at all interested in taking back several dozen cases of plugs he had special ordered in for me at my request (and I don't blame him), so I ended up giving them all away over the years to those community organizations that keep showing up at businesses asking for donations for their fund raising events. So if you have a plug that works well for you, just keep using it.......I really don't think you'll find any plugs out there that will make a dramatic difference in performance or fuel economy. But some people must sure love those Bosch W150M11S plugs that I mentioned in a previous post. I put four of them on ebay a week and a half ago and they sold for somewhere around $45.00....I don't think the buyer was planning on using them in a motored bike engine.
  18. locoWelder

    locoWelder Guest

    I'm useing the same plug right now and I like it, It dosen't foul out like the cheap plug that comes with the motors,now as far as mpg, i haven't seen an improvement yet
  19. Herrmanator8

    Herrmanator8 Guest

    diamond fire E3, best spark every time, full burn, no fuel wasted.

  20. davidsis

    davidsis Guest

    I just installed a Champion CJ7Y low profile. Wow what an improvement. Kind of smaller than the original though.