Variety of Issues with a MXZ 670

SKS_guy · Dec 3, 2007

Hi

My girlfriend went out and bought herself a sled this fall. It is a MXZ 670. I took it out and looked it over this weekend and had a few issues. I should say that we rode this sled last year and it seemed fine. I put fresh gas in it.

1) horrible time to get it started. Once started it would not remain running with out extra shots on the primer every 10 seconds or so.
2)was only running on one cylinder, give it gas and it would bog out. Changed spark plugs with nochange.
3)Limp it out to a open field and pin it, it bogs a second and then takes off like a shot, runs great. Keep revs up 1/2 throttle and above. When you let off and then hit it again, it bogs for a second then goes.
4)After a 5 minute run I stop and let it idle and idles well, revving pretty high at just under 3000. Not bogging as much when throttling up.
5) let it sit for a couple hours and then warm it up as before, need extra shots of primer to keep it going.
6) Take for a longer run, cruising across a smooth field at about 50MPH about 2 miles and it completely shuts down...dead. Pull it over some, seems to be pulling very tough. Pull Pull Pull....not firing ...dead.
7)load it up and Haul backto town. Give it a pull or two. small firing, but pretty dead.

Any suggestions as to what to look at to fix up these issues

Mod-R · Dec 3, 2007

1. clean the carbs first, get fresh fuel, put some seafoarm in the tank. If its been sitting to long you have to replace the fuel lines and take the tank to aradiator shop to be cleaned out. Try cleaning the carbs,fresh fuel & seafoam first.
2. If you have not had a rotary valve ski-doo with a primer before here's the deal on cold starting. ON a 670 when the motor is stone cold give it 4-5 FULL primer squirts and leave the primer out, if it starts and stumbles give it a quick shot to keep it running. IF it DOESN'T START DON'T GIVE it any more primer or you'll flood it, just keep pulling until it fires. You don't want to flood
an RV Ski-doo motor, you be pulling for a long time. Usually after the sled is warmed up you don't use the primer any more unless the motor really cools down like stopping for lunch, then you want 1-3 primer squirts max, not the 4-5 you used when it was cold or you'll flood it again.
3. While you have the carbs apart make sure it has the float arm/ level update this will help with flooding in down hill, off camber situations. Try and park on the level or pointed up hill this will help not flooding when your stopped.
4. These little quirks the 670's were the HP kings of their day. Polaris had to
come out with the 700 RMK twin motor to take the Jackson Hole Hillclimb
title for stock sleds back away from Ski-Doo. THe motors are also reliable.

If your still having problems after all this take it to someone who knows ski-doo's and have the Rotary valve inspected/timing checked.
Good Luck

Tdubbs · Dec 3, 2007

If you only stated the idling issue I would be going straight to the carbs and cleaning them an erratic idle would probably be directly linked to a plugged pilot but I'm guessing that you either developed or had a pre-existing crank issue...probably started with a crank seal leaking causing it to idle erratically as you stated and ending with a light lean seizure as you described...do both a compression and a leak down test on the motor you may find your problem there.. Please post when you discover what it was...The 670 was a great motor but not without its inherent problems one being the crank...

akx · Dec 3, 2007

do a compression test it sounds like you might have a broken ring.

SKS_guy · Dec 18, 2007

Hi Again,

We took your advice and did a compression test, One side was at 90 the other was at 15. We took it to the Ski-doo shop to have it fixed. They figured it was a ring too, but we have to see once they open it up.

I will post more once I know more.

Thanks

NoSecondChances · Dec 18, 2007

SKS_guy said:
Hi Again,

We took your advice and did a compression test, One side was at 90 the other was at 15. We took it to the Ski-doo shop to have it fixed. They figured it was a ring too, but we have to see once they open it up.

I will post more once I know more.

Thanks

90 and 15? Sounds good, can't see why it didn't run

...was this cold or warm compression test? Build it to a 740......Then let the G/F drive it around! LOL!

SKS_guy · Jan 22, 2008

Got it Back Finally

Hey

Just got this sled back, it was in the shop since Dec 15th. They replaced cylinder and piston, rod etc. It cost $1300+. Does that sound high?

My Girlfriend is a bit upset, she is having a monir surgery in a couple days and she may never get to ride her sled this year.

Thanks for your help on this.

SKS_guy · Jan 27, 2009

More Trouble

Hi again,

We got out on this sled once last spring maybe 10 miles. They put oil in the gas. It ran OK, but still had troubles getting it warmed up and going. When we picked it up from the shop, it took forever for it to warm up emough to get it on the trailer.

Stored it away, we put fuel stabilizer in it.

We took this sled out a couple weeks ago and could not get it running properly, would not warm up and we had to constantly prime it to keep it running. We were out with some buddies and they had an extra sled so we didn't mess with it.

1.5 weeks ago I took it out. It took forever to warm up and it was a relatively warm day. Had to keep priming it over and over. Eventually it ran well enough to get it to move. I took it out to a field and putted around, still having to prime it on ocassion if I let of the gas. I got it up to half throttle. Things come to a halt just as before. Try to pull it over and it is tough to pull it over. Pissed off we haul it back to the trailer. I suspect that another piston is gone.

We take it back to the dealer. After a bit they pull the carbs off and say they are dirty, they had cleaned them the previous spring when we had it in there. No way to know if they really had or not.

I asked them if they had checked a couple of the issues suggested here, in particular the crank seal. They said they did. They say our fault and they want even more money to fix same issue.

Any suggestions as to what could be wrong?

Do you think the dealer is dicking us around?

Any suggestion as to how to approach them?

I am just really pissed off.

Thanks guys

NoSecondChances · Jan 27, 2009

Where are you located?

Unfortunately, the money that you dumped into it is more than what its worth.

If it was me, before I took it anywhere the second time now, I would be pulling carbs off, and pulling exhaust off and head off and cylinders off (2 hr job). If there is nothing broken (rings and pistons OK) then it has to be timing or fuel. After this I would fully dissassemble the carbs and thoroughly clean them. Then I would put it back together and check timing. They are a pretty sure fire motor and pretty simple. Biggest thing is the RV timing if you take it out, but I wouldn't go there yet. Did it break a ring again?

Let me know.
NSC

SKS_guy · Jan 28, 2009

I am in Regina SK.

Does anyone think we have a leg to stand on in going after the dealer to fix this or at least help out?

Thanks

NoSecondChances · Jan 28, 2009

Hard to say, because it was so long out of the shop not really IMO. I believe that you only rode it a couple times but they can easily cop out and say taht they think it has been ridden dozens of times since it left there and they are not responsible. Unfortunately sleds are not one of those things that warranties are easy to follow up with. You might try the soft approach before threatening with lawyers.

What is the problem? Broken ring again? If its the same side and a broken ring you might have more ammo to back it up saying they didn't fix the problem. If its something else this time or the other side, I don't know.

Hope you get it fixed.

NSC

SKS_guy · Jan 28, 2009

The piston was melted the first time, they said it was too lean.

We have tried the soft approach on the whole deal. It took them way over a month to get it fixed the first time due to personell issues at the shop, which we were patient with, they said becuase we were patient they would make sure to give us a deal. They quoted us $1300, tried to charge $1700, but settled on $1350.

I realize that it has been a year since the work was done, btu if they check the speedo is shows only 10-20 miles. The gas and oil they put in is still there.

When we picked it up last spring it took forever(10+ minutes) for it to warm up so it would move and that is the same issue we had before and continued to have. We were told that this is normal. In talking to a couple of 670HO owners I confirmed that a 2-3 minutes was normal.

I think they missed something.

Do you think that the carb would get dirty after 10-15 miles and then sitting for the summer? I question whether they cleaned the carb.

Who knows?

I don't expect them to fix the whole thing free of charge, but they are wanting to charge us way more the second time. They say 10 hours labour at $100/hour + parts

jjmyzrider · Jan 28, 2009

I used to own a 1996 Summit 670 and had similar issues. I bought the sled in 1998 used, come to find out after buying the sled and having it a few months the old owner had problems melting a piston in it. I melted a piston in it on my fith ride, and rebuilt it myself. I was having problems getting it started and I knew that they were hard to start, and since it was new to me I assumed it was just the way I was doing it. I also noticed irratic idle speeds, no consistancy to it at all, thought and was told to change crank seals, so I did when it was rebuilt. After putting it all back together, I fired it up in the garage. It was over-reving really bad, enough to engage the clutch. After looking everything over very carefully I noticced a frayed throttle cable. Since it is a split cable for the carbs, one side was always out of sync with the other. I replaced the throttle cable and ran the sled many hard miles and never had an issue with the engine until last winter (1/2008). I rode nine years on it with no issues, as far a engine issues. That is one thing to check, and it may help. The one thing that does not make since is the time it takes to warm up. I have no suggestion on that, also if you need to dump another $1000 in it you might just sale it for what you can get out of it and find something else, I chose to sell my sled rather than fix the old one, but I had a good sled already and didn't have to buy one, might be something to consider. good luck hope you find this helpful.

NoSecondChances · Jan 28, 2009

SKS_guy said:
The piston was melted the first time, they said it was too lean.

It is another melted piston and is it the same side? If so, its gotta be jetted wrong or there is a leaky intake or crank seal.

No the carbs should not be that dirty after only riding a few miles.

Yes they do take that long to warm up. The MXZ has big coolers and it takes a long time to warm up. My 670 takes at least that long and it has the MXZ coolers on it. It takes mine at least 8 mins of idling to register on the temp gauge. It should still go without being warm though, technically it should fire up and you can ride it away 10 sec later (not advised but possible). If its not moving until it gets warm something is wrong internally (like it doesn't have enough power). If you couldn't load it at the shop because it wasn't making enough power then they didn't fix the problem the first time.

Seriously though, you can fix this sled yourself if it is a piston. They are super easy to work on. Get a transfer pump from Princess Auto or Crappy Tire and suck the coolant out of the tank and out of the lines, then pop the head off and have a look. If you need to know how to pull it apart any farther than this, PM me and I'll give you a call and tell you how to do it. I can do both cylinders on mine in an afternoon.

Think of it this way - What have got to lose??? Worse comes to worse you end up with a broken sled right?

SKS_guy · Feb 9, 2009

Update

Hi all

We ended up taking the sled from the dealer and taking to another shop. We tried to work out something with the dealer, we offered to pay for parts if they would pay for labour. They initially said no then yes and then only half the labour. They said they would not be responsible for anything else after it left the shop, they never wanted to see this sled again. They admitted that the shop was in turmoil last year when we had it repaired. All the service dept has been turned over. We challenged the the carb may not have been cleaned last year, they agreed that this may have been a possibility.

We took the sled to another shop and they have tore it right down and found a burnt piston, one side was melted. Cyclinder walls are relatively unharmed. They found no other problems.

What jetting should this sled have? Our elevation is about 1900'. We don't want it even close to leaned out.

Will running it out of gas in the spring before storing keep the carbs clean. Turn gas tap off and let it run?

What is the process for cleanning the carbs?

Thanks

banditpowdercoat · Feb 9, 2009

The stock 96 Summit 670 had 380/370 main jets PTO/Mag sides respectively, with 40mm carbs.
The 96 Mach 1 670 with 44mm carbs used 420/400 Main jets.

Your elevation, I would start with 390/380 or maybe even 400/390. Can allways lean out if your to rich. No sled blows a piston from To Rich.

As far as the carbs, Yes, at the end of the season, shut fuel off and run engine untill carbs are dry. I acctually pull the carb drain caps and drain them. Fuel will make Varnish and will plug up carbs when it evaporates over the summer. For cleaning, Just take the carb off the engine, an take the bowl off. Do over a cloth or somehting. There are some small parts that may fall. Clean with solvent, or carb cleaner. Blow all passages out with air. Good idea to take jets out, examine that they are not plugged. Re assemble and put back on engine.

winter brew · Feb 9, 2009

I would replace the pilot and main jets in the carbs...cheap! Also a good disassembly and cleaning of both carbs. I would also replace the fuel pump....they do go bad and again....cheap insurance. No fuel pressure=burndown. Also look for a kinked fuel tank breather. Pull the fuel cap and blow into the tank, it should not build any pressure, you should hear air coming out the breather. A plugged/kinked breather will also starve it for fuel=not run, possibly burndown. Also, some sleds in that era had a cone shaped filter in the carb, right at the fuel inlet. they were supposed to be removed after a tank of fuel. Alot of these for left in and they WILL clog and also cause a burndown.....just a few simple and cheap things to check!

Red-eye · Feb 9, 2009

Check all the jets and needles in the carbs as they may have been wrong. And yes the carbs can get dirty and clogged through the summer.

NoSecondChances · Feb 10, 2009

winter brew said:
I would replace the pilot and main jets in the carbs...cheap! Also a good disassembly and cleaning of both carbs. I would also replace the fuel pump....they do go bad and again....cheap insurance. No fuel pressure=burndown. Also look for a kinked fuel tank breather. Pull the fuel cap and blow into the tank, it should not build any pressure, you should hear air coming out the breather. A plugged/kinked breather will also starve it for fuel=not run, possibly burndown. Also, some sleds in that era had a cone shaped filter in the carb, right at the fuel inlet. they were supposed to be removed after a tank of fuel. Alot of these for left in and they WILL clog and also cause a burndown.....just a few simple and cheap things to check!

Excellent pointers there^^^^^.

You can find the high altitude specs for your sled here:
http://stboni.com/download/mmt9802a.pdf

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Variety of Issues with a MXZ 670

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