| Author | Message | ||
     Oldbike |
I bought my m2 used but the owner had ridden it hard. I knew that but it was a good price. I pretty sure the carb needs to be tuned to match the cam. But anyways at idle and not in gear I can give a quick blip on the throttle and smoke will fill the air. not blue or black just a haze gray color. I can rev it higher with not much smoke if any. Its just that quick blip on the throttle that causes smoke. only smokes on decel Swingarm also has a nice black chare on it. So whats your guess as to the problem and how to fix it  Hopefully is cheap and easy -- wife isn't to happy about the bike. I've got a leakdown gauge that I want to use.. Having never used on before. Is the piston supposed to be TDC or BDC? (Message edited by oldbike on July 13, 2005) | ||
| Steveford |
Valve guide seal flopping around uselessly on the stem would be my guess. | ||
| Buelliedan |
Does it have a Thunderslide in the carb? If so it shoots a ton of gas into the carb when you gas it due to an increased fuel shooter in the accelerator pump. My S1 does it as well. Too big of jets could also be a cause. | ||
| Oldbike |
I was thinking either rings or the valve guide seal myself. Never tore down a engine--- so I don't have the knowledge. Would the leakdown test show which head has the bad valve guide seal? Can the heads be pulled with the engine in the frame? That would be great simply pull the head and let a pro fix the problem then I just put it back on. | ||
| Oldbike |
Mukuni 42 carb. Unknown jet sizes. I kinda know how to tinker with the mukuni. thanks | ||
| Bomber |
heads can be pulled without droppin the mill -- check your plugs for deposits -- black/oily, head work at minimum -- compression, or better, leakdown test will give you a good indication as to the problem . . .. in order of easiness 1 check plugs 2 compression test 3 leakdown test 4 sit on milk crate and zen as to symptoms/fixes | ||
| Tramp |
first- leakdown will show which jug/head has issues. second- if the smoke is billowing upon twisting of throttle, as opposed to coming down from higher revs, that eliminates a few causes. when you state :"smoke will fill the air", is it thick, hard-to-see-through smoke, or is it misty, and, does it SMELL like burning oil or sweet and gassy? There's a good chance that the carb is the culprit. The mikunis , when incorrectly set up, canpour the gas into there and you'll get that sweet-smeeling rich mist, as opposed to the bitter, rank cloud of burning oil which a ring/valvetrain issue would create. either problem is a breeze to repair, so relax. i didn't check your profile, and according to what area you're in, maybe someone onboard can recommend a decent shop, if you prefer not to tackle this one yourself... | ||
| Oldbike |
changed plugs yesterday. front plug is oily-black-sotty, rear plug is dry black. i'll do the leakdown test once this nasty weather clears up. | ||
| Tramp |
wait a sec- what did the front plug SMELL like? oil or gas? also- run it with 2 NEW plugs, and recheck them for smell and appearance- if the last owner was blasting about with a mistuned miknui, you could have severe deposits on the plug(s) | ||
| Oldbike |
2 new plugs are in the bike and I'll do as told. ride, recheck and smell. | ||
| Bomber |
now THERE'S an image I didn't need ;-} | ||
| M1combat |
Is there an accelerator pump on that carb? | ||
| Oldbike |
Always do a sniff check before i ride  Rode the bike for about 20 minutes. Rode fine. A/F gauge shows lean at idle to soo lean not even on the gauge. At any thottle % its on the first few bars of rich. Get back to the house and rev it up. Smoke only comes out after the throttle is returned to zero. Doesn't matter if I rev slow or quickly. Once I release the throttle some smoke is let out. Don't have time to check plugs. Eating, getting dressed and typing all that the same time. Had t get a part time job to pay for the bike and my gym habit  | ||
| Bob_thompson |
John, only my opinion, but in my experience, with smoke coming out on engine backing down sounds like intake valve guide\and or seal if there is one. When letting off of the throttle a higher vacuum is momentarily produced in the cylinders sucking additional oil in through that guide producing the smoke. Usually doesn't happen at steady RPM's. The oily black on the front plug denotes oil and the dry black on the rear sounds like the engine might still be running slightly rich somewhere in the rpm's. If valve seating and rings are in good order leakdown test won't show much. Pulling the head to inspect guide to valve stem clearance is probably in order. Bob | ||
| M1combat |
Yeah... Same here. Intake valve guide. I didn't realize it was only on decel... | ||
| Bomber |
agreed -- decel generally indicated a bad Valve Guide/Seal | ||
| Bluzm2 |
Old, I would also suspect the valve seals given the information you provided. However, also check the jetting on the Mikuni. The HSR 42 on a M2 motor should be around 30 pilot and a 160 main. That's how mine is set up anyway... I currently have mine torn down as I need to replace the rear base gasket. Since I have it apart, I'm going to do a quick hone and a new set of rings. Probably give the valves a quick check too. If the guides are OK, just a quick lapping and new stem seals. As has been mentioned in the KV, the exhaust seals are prone to leakage after a while. Particulary the rear due to the higher heat. I should have mine back on the road this weekend.... BTW, these old lumps are very easy to work on. Kind of fun too! Pick up a service manual is you don't already have one. Brad | ||
| Tramp |
That's why I mentioned, 12 posts back: "first- leakdown will show which jug/head has issues. second- if the smoke is billowing upon twisting of throttle, as opposed to coming down from higher revs, that eliminates a few causes." once you pull the fresh new plugs, the story will be told in full- you see, when you have old plugs, regular fuel fouling (as in an ignition issue) will appear oily, as it mixes with the black carbonic residue. on a fresh plug, it'll appear clear and simply 'wet' or else black and easily wiped off. fouling due to rich mix (misadjusted carb) will appear black and rather satiny. oil fouling (due to guides, valves, rings, etc..) will be, well....dark and oily..this is an excellent diagnostic procedure. obviously, I agree that the likely culrit is a guide or a seal around a valvestem or two. before pulling the topend, however, PLEASE do a close inspection of the fresh, low-mile plugs. fuel mixture issues can still cause post-rev misting/smoking, as can misajusted timing(!). | ||
| Bob_thompson |
Right you are Jay and simpler fixes are always better and cheaper. | ||
| Newfie_buell |
I got three four stroke dirt bikes and they DON"T smoke. | ||
| Tramp |
umm....Ok.... I'm a four three year old and I don't smoke.... | ||
| Oldbike |
Thanks soo much for the input. I'll check the timing, and do a compression test then that will give me some more data. if its the valve guides. I looked at the manual and I "think" I can pull the heads at least with the help of the board. Then just send them to Nallin for fixing. It will have to wait till winter -- I want to ride the bike for the summer time. ________ leakdown testing should that be piston TDC or BDC? | ||
| Tramp |
pulling heads is a bunt. you don't have to ship your heads to a tuning firm like nallin to resolve your issue. any competent machine shop (check your yellow pages) who has worked on evo heads (most have) can perform this simple and inexpensive repair. |
