I am new to snowmobiling and bought a 1998 Mach 1 for my wife. Starts first pull, runs smooth but yesterday when I started it there was some distinctive knocking in motor at random times while it was warming up. It didn't do it when I gave it some throttle but did it when running at 2000 rpms...thoughts?

Start will the simple obvious stuff, check the plugs, put brand new ones in, and be sure they are the correct ones. Sometimes on a used sled, some yahoo will but the wrong plugs in.

While changing the plugs, make note to look down the plub hole with a flashlight, and make sure that there is no garbage or metal flakes from a bad piston or ring.

Are you getting proper oil lubrication. If you dont know alot about sleds, just check your oil reservoir, you should be using roughly a 1/2- 3/4 quart of oil to a full tank.

If its carburated, which is probably is, clean the carbs. If you dont know how to do it, at least buy some K100 and some fresh fuel and just run the thing. Sometimes water or gum can build up giving you a rough idle and poor performance.

Lastly, check you airbox, make sure its clean and free of mouse droppings or nests. Lack of air will cause the engine to load up and stall out, pop and run like crap. Used sleds sometimes are stored in poor conditons and Junk gets in the air box

air box is suspect to me from your symptoms. Its easy to fully remove it, clean it out and re-install. Where the airbox attaches to the carburator, check the rubber boots and make sure there are no cracks. Sometimes that can cause issues too. Simple setup, you need Air, fuel and spark for an engine to run..... start with the simple stuff, clean airbox for air, new plugs for spark, and new fresh fuel with K100 in it. I would bet one of these things are the problem.

DJ he says the motor runs just makes a knocking sound a few time at low rpm so the motor is running and runs fine at higher rpm. A knocking sound at lower rpm could be in the primary clutch before it starts to engage? or something is loose. If it was bad spark,fuel or air it would bogg or stall your hearing a knock.

Thank you. I will start with these suggestions. On another note, the sled has the low winshield on it and I was given the tall one as well. In order to remove the windshield I see what appears to be black caps over some screws. Am I correct or are the caps/screws really one time snap in plugs?
How do I remove them? Do I need to drill them out or are they truly caps that I can pop off with a small screwdriver to gain access to what I am hoping is a screw head.

I don't think you want to drill them out. They are probably plastic "darts" that pop in and out. Try gently prying with a screwdriver and see if they come out.

My polaris did the exact same thing, the old one I sold. It ran ok with full throttle, but at idle popped and sputtered. I found a mouse nest. Maybe its something different.

Yamdoo, the windshield, yes those are made to pop out with a bit of prying with a small screwdriver. Most of the time, if you pop the center of the plastic rivet, the rest will follow. I personally would just buy a few new ones, sometimes they get brittle with age. They are cheap, you can get them at a hardware store.

Well that's what we need to now? Is it a pop like a backfire or a knocking clucking sound like metal on metal.

The sled I just traded in, I thought the engine puked one day, I was coming down a hill, and heard a loud rattling, like metal on metal. What I found was the exhaust heat sheild straps broke making the heat sheild rattle like crazy on the pipe, but the wierd part was that it only happened at certain RPM"S. I clamped the sheild, and back in action.

My engine was knocking, like it was a timing issue or that low octane gas was in the tank and you gave it heavy throttle. I filled my portable gas tank with Premium and put the same gas into my Yamaha as I did in the Ski Doo. Both need premium gas, only the Ski Doo is knocking.

I bought them both used this year as an entry into snowmobiling. The Yam is a 1998 SRX700.

Sounds like you need to drain the tank and start from scratch with new fuel. Bad gas WILL toast your motor.

These are 2 stroke and don't knock like a car. also running higher octane in the sled will do nothing unless you have the compression to run it. I run 87 in my new 1000.

Interesting. The only thing is the SRX700 has the same gas in it's tank and it's not knocking.

agreed, I run 87 octane in my new 800R too. The manual states "use 87 octane unleaded fuel only" "use of fuel with an octane rating higher than 87 can cause engine damage".
But the new 800HO motor requires 91 octane or higher.

Yamdoo, do you know how to clean the carbs? If you do, and you already tried new gas with gas treatment and new plugs, it cannot hurt to try it.

Mine says to run 91 or higher, but has a detonation sensor to adjust for lower octane fuels.

Yamadoo, Where are you located ?

My old polaris touring sled had that too. Two clicks on the key, 93 octane, one click for 87.

East Brookfield. I joined both the Spencer SnowBirds and Colbrook clubs. I joined Spencer since those trails are close but I rode on the Colbrook trails and enjoyed SR71 so I joined Colbrook as well to directly support the club that manages those trails. Just got the sleds this season, haven't done any club events.

Yamdoo, do you know how to clean the carbs? If you do, and you already tried new gas with gas treatment and new plugs, it cannot hurt to try it. - Don't know how to clean the carbs. I'll take a look at the plugs. I can order some from the local auto parts store or Motorsports Intl in Auburn. Suffice it to say I am no longer mechanically savvy though I suspect I will become so again.

OK somebody from that area step up and give the newbie a hand..At least somebody who knows a little bit. These are the things that make a good club a great club..After all it is his wifes sled. I noticed that pictures really get em going YAMADOO

I am from Wales, did you ever ride the Mill Valley system out of Belchertown. Its actually a pretty good trail system, but snow this winter has not been in the clubs favor. I really want to ride Belchertown this year, they buldozed the rail bed and really cleaned up this year.

Its a Ski doo. If you want some answers try and get the King to answer you. He's the master of ski-doo's.

Agreed

I agree about the KING. At this time we have gone from being a clutch problem to cracked boots to carbs. Somebody with experience needs to look at it.

Take it easy stimpy, folks are just giving suggestions to help the poor guy out. I gave basic suggestions becuase most of the time, its a simple solution to a minor engine issue. Remember too, that Yamdoo admitted he is not mechanically inclined, so it wont hurt for him to learn how to do some of this things recommended just to get familiar with the sled and general maintance. I am no mechanic, but have learned alot from tinkering around, listening to folks, getting advise, and actually making friends that have some expirience and watching what they do.

Thank you everyone for their help with providing some possible answers. I picked up a set of NGKBR9ES's at lunch today. Hopefully I can try to put them in tonight but I may run out of time with some house stuff I've got to get done before the w/e. I'm hoping to get the plugs replaced and gas drained first as that seems to be the best place to start. If I can get these done this week my wife can try out the sled on Lake Lashaway this w/e to make sure evrything is good to go.
If anyone is local to East Brookfield I'd always appreciate the hands on insight and tips. It would be great if at some point I had another set of eyes looking at the sleds to tell me what needs to be done to them.

I attached a bad cell phone pic of the two toys. I'll have to get some better pic to put on the profile

Skidoos have a bad crank bearing design. They have plastic "cages" (plastic rings with pockets for each ball bearing)... It's not uncommon for these plastic cages to fall apart over time. The result is bearings inside the engine rotate as the crank rotates, but the balls bang into each other.

To check if this is the case on your sled:
quiet location needed...
hood open, engine off... Rotate the engine by hand turning the clutch... listen closely for the tell tale sound "clink, clink" as the ball bearings roll into each other. If you hear this, you need to split the engine & replace the crank bearings & seals. Do it before the sled blows up.

Don't confuse the "clink, clink" sound your going to hear from rotating the clutch... There are weights in the clutch that will make that sound even though the clutch is good. (note: 3 clutch weights, equally spaced @ 120 degrees = 3 notable "clink" sounds per full revoloution of the clutch)

If infact your crankshaft bearings cages are bad, the "clink, clink" sounds are notably different than those you'll hear from the clutch.

Does the motor make the noise after it's warmed up, or just when it's cold?

The extent of my snowmobile riding has consisted of 1 day on the Spencer area trails last year, 1 day on SR71 from Oakham to NH, maybe 6-8 days of riding on Lake Lashaway (my home) to get used to the Yamaha and one day each in VT and NH over the past few years. I am truly a newbie, but a very excited one, eager to ride and learn..but I'm also a middle age newbie which brings it's own set of time challenges. I am really looking to get into snowmobiling and hope to get my wife into it also. That's why I want to get the Mach 1 running flawlessly for her.

I totally agree..It sucks for a gal on a sled that's not running properly. If it's not fun they don't want to go. The best advise that I can give you is,.... GO BUY A BRAND NEW YAMAHA. She will love the sport and want to go every day

That's my "long term" plan...but financially I needed to start out inexpensive, which I'll admit is not always inexpensive overall. If all goes well and we dive into the sport then 1 or 2 newer sleds and a trailer will appear down the road.
Kind of like boating or automobile racing, buy what you can initially "risk" and then if you see a emotional return on it...go bigger/better. I must say I do love my SRX700. Need my wife to love her Mach 1...

Any fool close enough to East Brookfield want to swing by one evening or weekend time to give me a diagnosis?
The bad thing is, no heat in the garage so all I have is a space heater available. The upside, food and beer and that warm fuzzy feeling of helping someone out who doesn't have a clue.

If you want your wife to really like the sport getter her a Mach 1 may have not been the best sled to learn on. The mach 1 is alot of machine and heavy. Just riding that sled may discurage her on getting an other one.

agreed, get her a light weight fan cooled sled. She can ride all day, nice and slow, never overheat, and if you get like a Cat F570 twin spar like my wife has, she will be able to keep up, and not get tired in the trails.
F570, brand new leftover would be no more than $4500.00 A bargin for a new sled.
Even a Fan cooled Polaris 550 with the M10 chassie is a great learning sled, and comfortable. YOu can find those anywhere a year or two old for like $3400.00

My wife loves her sled, even after the accident...>LOL

Too late now. It's "prettier" than the SRX700. I'm looking to get a year or two out of it and then she will want a newer 2 up to ride. Besides, she likes the speed of the Mach 1 triple even though she won't take advantage of it regularly. She had my SRX at high speed on the lake a few weeks ago when the snow conditions were right. Once she gets past the need for speed and wants a lighter handling sled for trails, then I can make the change and get her away from the Mach 1 as she also wants elec start and reverse.

Just a note on the 2-up sled I own one also and my wife won't drive it is big and tippy she rides a 440 and loves it. 2-up's are nice to have when you have kids that what I take when me and my son go out.

Or with the boys when its running ok....LOL

I could see my wife and I on a pair of 600's in a couple of years, a single and a two up.

Have a 12 yr old son so we would need a two up...thinking about it, this means I'll be on a two up in a couple of years and my wife will be on the single.

12 years old, in Mass, he is legal to ride on his own. Legal in any state park and private land provided that he is not crossing a road. Road crossings, he needs to walk, and a parent or guardian needs to ride the sled across the road.
My nephew is 12 years old, rides my wifes F570 better than I can. Get him his own sled and teach him on the lake near your house. You will be surprised how well he will ride. Ask Grasshead, his son handles a sled very well.

He's ridden my SRX700 with me sitting behind him. I'm doing it on the lake with him as you suggest because it's much harder to hit a tree in the middle of a snow covered lake, which is nice. I'm working with him to get him to look ahead and to be smooth. He's, of course, interested in exactly how fast the speedo says he's running. I need him to see a patch of uncovered ice (as if it was open water), or a rock on the shoreline he may be travelling on and plan anvoidance route. The next time I get up to SR71 with him, whenever that will be, I'll have him do some front seat time in the open trails and have him keep the speeds low and get him to relate to how the sled feels, how it smells and sounds, how the track is reacting, get used to the steering or lack thereof and to always plan ahead and NOT DRIVE BY SPEEDO.
For now being on a 300 acre frozen lake, he hasn't had to do that and I need to get him to that level. The problem is he's not afraid, or should I say respectful, of speed at this point.

LOL, they never are afraid.... Thats awesome he is learning. I taught my nephews on an old Polaris 400 fan. The sled was slow enough that it kept them out of major trouble. My neighbor just bought his 11 year old a Cat ZL 370. He paid 800.00 bucks for it, and its top end is about 60mph. The kid absolutely loves it, and rides with us on his own now. The key is to teach them to respect the machine and the surroundings. Explain the consequenses of being and idiot, and lead by example. With teaching my nephews and my neighbors kid, we always kept them behind us, and really took our time. It taught them throttle control becuause they wouldnt want to hit us.

I have to agree with most here. That Mach 1 is going to be ALOT of sled for your wife to learn on. It's very powerful, heavy, and the suspension is not very forgiving. Might want to try putting a hose clamp on the grip behind the throttle "just in case". If she freaks, she can't grab a handful and end up in the woods.

Fortunately, or unfortunately, depending how you look at it, I introduced my wife to high speed cars when we met so she drives our current sports car daily except when it snows and she respects the car as she has driven some of my previous monsters. I went from being the daily driver of my sports cars to the one driving the SUV so she gets the fun machine. You can see a corner of the current sports car in my snowmobile picture but it's in it's winter garb so it looks like crap. She's been a passenger on Daytona before a Rolex24 race and we considered getting into the club racing scene as we have friends that do it in FL but the prospective group of novices at the time turned her off. People with too much money who wanted to build full blown track cars down to the stickies before they mastered driving their street legal cars with street tires.
If the weight of the Mach 1 gets her, I can get her hooked on a lighter sled down the road. Same goes with the suspension. My Yam came with an Ohlins set up, handles fine. Her Mach 1 definitely doesn't handle the same from what I could tell in one ride but her track is in better shape which helps.

For now, I've got to figure out the mach 1 problem and right it.

Wife had a flat tire last night on the way home so I'll try to get to the plugs Thurs/Fri evening and see if that corrects it. For humor, I started the Ski Doo when I walked into the garage last night and it didn't knock for the 30 seconds I had it running. It did sounds like it was occassionally skipping while idling at 2000 rpms, which is totally separate but that could lend to the bad plugs - bad gas theory.

put some K100 in it, new plugs, and run the crap out of it. YOu will be fine after this weekend.

here is how you test for a bad crank seal. Get a can of starting fluid and then take off the clutch guard. Start the sled and let it idle. Spray a small amount in between the clutch and the motor if the motor idle changes you have a bad crank seal on that side. This side is usually the first to go because of the clutch.

INTERESTING

Good tip.

There's usually more than one reason a leader becomes a leader in the 1st place...

Looking on the K100 website, they don't show any central MA resellers. Where do you guys buy yours?