Clutch Rear wheel locks with clutch engaged unless I remove spark plug?

Discussion in 'Transmission / Drivetrain' started by Fletch, Nov 9, 2010.

  1. Fletch

    Fletch Member

    When I have the clutch engaged without a plug in I can push the bike and the engine turns and piston moves freely. When *any* plug is in, the rear wheel is almost completely locked. It takes a lot of force and skids along, but it does turn kind of randomly with much force.

    I know this is normal to have resistance with the clutch engaged, but this seems like way too much. I came across this because I have had trouble starting the bike recently. When I engage the clutch it isn't firing right up like it used to and I notice the drag of my rear wheel locking. If I keep pedaling and give it some throttle, I can usually get it going the 3rd time, but it isn't an immediate's kind of a gradual build up as I pedal and throttle.

    I thought it was a plug's not. I thought it was a carb issue...(doubting it now)... then I thought maybe it was something damaged internally like a broken piston ring causing extra friction. I opened it up and everything looks normal?

    Thanks for any help in advance! I'm really not sure what to try next? I'm thinking maybe the clutch, but I read that if it was the clutch, then the engine wouldn't turn at all when pushing?
    Last edited: Nov 9, 2010

  2. HeadSmess

    HeadSmess Well-Known Member

    like, sounds like the plugs tooo long... you say it

    wwwwwwierd :p
    are you sure its not the plug? like, try a lawnmower plug with a shoooort thread...

    how far did you "pull" it apart? im thinking maybe rod bearings siezing up under compression loading...maybe...

    *scratches head*
  3. Fletch

    Fletch Member

    I know... It is weird! I tried 3 different plugs including the Chinese one it comes with. The first plug I used on this bike was the NKG iridium plug which is way longer than the stock plug. I was afraid it was making piston contact, so I took a look. It wasn't, although there was a bunch of sticky 'gunk' (for lack of a better word and mechanical knowledge) on the side the plug is on (slant head). So I cleaned it off and added some washers to the plug to back it out some.

    When I was looking through the plug hole at the piston coming up, it looked really close though! It looked like it could definitely be hitting. No marks on the piston, and no bent or closed gap plugs though! I even screwed in a plug about half way to make sure about contact. It seems that just blocking the hole causes too much pressure.

    I really didn't pull it apart. I just took the block off and looked at the piston and where it connects to the rod.

    I'm really afraid you're right about something causing it to not handle compression. So you think the bearings maybe? I'll do a search because I have no idea how to address that. I've been pushing it pretty hard during the 'break in period' because I read that you should use WOT during break in by someone here and it gave me an excuse to go faster, lol. Maybe I did some damage?

    The strange thing is that once it's running, it RUNS! I'm hitting 35mph, with good acceleration and no problem with hills. I'm really confused and hesitant to take apart the engine.

  4. Al.Fisherman

    Al.Fisherman Active Member

    You say break in...maybe the rings are just now seated properly, and you have great compression. Do you have enough azz (weight) to spin the rear wheel to start. That was a problem my son had at 135#. What I did for him was add another head gasket. Take a compression test.
  5. Fletch

    Fletch Member

    haha...yep, 180lbs. Hopefully you're right. I already have 2 head gaskets on it too, because the head isn't completely flat and there was a visible gap until I added another one.

    I'll have do do a search for compression test.

    It's no problem really as long as the engine fires up as soon as I release the clutch lever. I think it is running too lean, so I'll play around with the carb and see if I can get it to fire right away.
  6. AussieSteve

    AussieSteve Active Member

    Fletch, I agree with Ron. It sounds like normal compression. (I'm 110 lbs and also used to have trouble turning mine over.) If the plug was hitting, as you mentioned, the plug gap would close up and/or the piston would show damage.
    From memory, the compression for a stock engine should be around 95-115psi.
    Screw the compression gauge into the plug hole, then pedal at starting speed for a couple of seconds with the throttle fully open.
    Hope this helps.
  7. Fletch

    Fletch Member


    Thanks for the instructions to check compression.

    Fortunately you guys were right and there's nothing wrong! It was just because the air/fuel was off and the bike wasn't starting right away that I connected the 2 things and thought there was a problem.

    I adjusted the carb and it fired right up today. It's running really well. It does feel like it's mostly broken in now after only 110 miles, but lots of WOT.

    On an OT side note... As I was pushing the bike along last night and listening closely to it... I experimentally put my hand on the gear cover plate and I was amazed how it dampened that 'whining' sound completely. I was reading how some people use mouse pads or buy the ones some of the vendors sell, but someone said they used cardboard on the inside of the cover. So I cut a piece of gasket material to fit the inside of the cover and rtv'd it on. It seems like it will make a difference from just banging on it with my hand. We'll see tomorrow when I ride it.
  8. Al.Fisherman

    Al.Fisherman Active Member

    Personally, I don't like to see 180# on these engines. 110# would be better for the engine and can be accomplished by adding head gaskets. This would also make for a easier start. 180# almost 2 X normal compression.

    Mill the head down (lay on flat glass or window and use 320 grit, only take off what is needed to have a shiny surface). Reinstall head and torque to between 120-204 (I use 150) inch pounds all this after I replace cylinder studs with grade 5 (metric grade 8.8)
    Last edited: Nov 10, 2010
  9. motorpsycho

    motorpsycho Active Member

    actually, i think he meant that he WEIGHS 180 pounds, not 180 pounds of compression.
  10. AussieSteve

    AussieSteve Active Member

    Been there, ....
    Rubber blocks between the fins helps heaps, too.
    See this thread: HT Engine Noise Reduction
  11. HeadSmess

    HeadSmess Well-Known Member

    ah, the old clutch cover singing.... i use my right calf muscle for that dampener :p

    anyways, you mustve got lucky and received a tuesday engine... :D
  12. Fletch

    Fletch Member

    Yeah, 180 is my weight.... :grin5:
  13. Fletch

    Fletch Member

    Thanks, that thread was a big help. I don't have any extra rubber lying around but I did have an old foam handle bar grip that I cut up and used between the fins last night.

    I'm going to test it out today. Hopefully the foam won't melt on me?

    Are your rubber inserts strategically placed (other than on the outermost part of the fin so air can pass behind them)? I'm trying to decide if I should copy yours exactly, or if it matters too much. I don't have any dirt bike experience or anything to go by.

    I used gasket material on the inside of my clutch case. To me it kind of seems like I mix between cardboard and rubber ;) Of course it is more expensive than free cardboard but I'm hoping/thinking it should work. Plus it gives me the illusion that I'm using all "high quality" components..
  14. AussieSteve

    AussieSteve Active Member

    I suspect that the foam will melt. Just try one piece first.
    Natural rubber is best. (Pieces of a car radiator hose would work well.)
    Regarding placement, it's not too important. I tried to put the rubbers where the fins extended the most and staggered them as much as possible.
  15. motorpsycho

    motorpsycho Active Member

    you want to cure that whine noise from the clutch the EASY way?
    Install a straightpipe with no muffler....the clutch noise will amazingly dissapear.
  16. Fletch

    Fletch Member

    Actually it didn't melt, but I'm not sure how much of a difference there was sound wise. Maybe my engine is on the quiet side already?

    Speaking of noise... Related to my bike being hard to push when clutch engaged... I have the clutch plate off to replace the gasket material with cardboard because the gasket material didn't make much of a difference muting the sound... and I think the 'clinking' sound that I hear as the engine turns is the gears.

    I was watching the small and large gear rotate and what it almost seems like is what would happen if your sprocket was out of round: tight and then loose. I can't tell this visually but it feels like it when I push the bike. It feels like the gears tighten up and then loosen as they rotate around, and the clink sound comes as it loosens. Does that make any sense?

    I am going to look into how to adjust the clutch. The bike still isn't firing right up. It takes a little while riding before it will idle at a stop too. Maybe the problem is in the clutch.