Summit 670 cutting out?

I know the HAC (High Elavation Control) was natorious for going bad, which is why they switched to DPM on the 99's. I would put new spark plug caps on, they have a resistor inside of them that can go bad, i would also check the teather contacts and make sure its seating properly on the housing (no dirt or snow inside cap). New plugs never hurt but will be hard to read what your engines doing until they have gotten a few miles on them. Cleaning out the carbs would help aswell, as for the HAC, not very knowlagable on that, i know when they go bad it can take your engine along with it, something to do with a inproper failsafe, meaning when the HAC goes it opens all the way or closes (cant remember which) and bassically gives the engine to much air/fuel (something along those lines). Not sure how to check it though... WinterBrew, Zachmandu and Wildcard are a few guys that know alot about 670's, also H2SNOW on Back... Country... Rebels.com(one word, no dots, snowest edits other sites, or atleast that one so you have to be tricky...) is a genius, if he cant figure it out, no one can. Someone else will jump on here soon, the site is gowing downhill so theres not alot of people on anymore... I think the compression is sappose to be around 130-145 PSI (not 100%, but somewhere in there).

Here I go again...

Need to know some things - Although both engines appear very similar, there are some differences. Did you use JUST the 670x engine? Or the engine along with it's ignition system, airbox, complete DPM system and carbs? Or did you install it with the stock 670 ignition, carbs, HAC, and airbox? It makes a difference.

If you used ALL of the 670x peripherals, it sounds to me like you may have DPM issues. Either the system is damaged/shot, or improperly hooked up...either wiring or vacuum hoses not hooked up/hooked up wrong. To delete the DPM, you need to change all the ignition parts with the std 670 ignition.

If you used the stock 670 stuff with the X engine, did you mix and match parts? That would be a no-no. Exactly which parts from which engine did you use?

What I would do, is install the std 670 stator, p/u coil and flywheel, and use the std 670 CDI module and coil assy. Then install the std 40mm carbs, deleting the std 670 HAC. When the HAC system goes bad (the internal diaphram is known to leak), the system goes full rich, and will generally turn the sled into a slug and foul plugs. After deleting the HAC, you can re-jet your carbs accordingly, dropping jetting to suit your altitude. I run 290/310's with 45 pilots at sea-level. For a performance gain, if you have the parts, you could run the X exhaust pipe, and 44mm carbs. Again, you would have to jet accordingly.

Somewhere in the S-chassis section I detailed out for somebody the steps to deleting the HAC. Shouldn't be hard to find.

As for the compression...... Live with it! Although, is it possible that a previous owner has shaved the head? That could contribute to it being harder to pull over.

Also, when messing with the carbs, be aware of which jets go in which carbs. It is easy to accidentally put the wrong jets in the wrong carb, or to switch the carbs side-for-side, which would cause one cylinder to run rich, and the other to run lean. That could cause it to do some really funky things with how the engine runs. On Rotax rotary-valve motors, the PTO side is the rich side.

If you have any questions, I will check back on this thread, or you can PM me.

What engine did you replace?? A 500? Did you put the 500 carbs and everything onto the 670? I assumed that you were replacing a std 670 with a 670 from an X.

Tell me in detail EXACTLY what you guys did. What parts were already on the 670, an what parts did you add from the old motor?

670 x

if you really want it running right you need to go all stock for summit X. the 670 X is high output and you cannot use 670 ignition and expect it to run right, even if you change it all to standard 670 like stator and brain and all. the 670 x is ported different timed a bit different and a few other things. Your best bet is to find complete ignition system for a 99 summitx including the altitude compensator. the 99 has a much better setup. Hvae been running mine for 10 years and never a problem. I would never get rid of the compensator. Many people do so they can lean out a bit to pull a touch more hp out of it but those are also the ones that need to rebuild quite often. Just my experience and opinion stay stock. they run hard as they are and if left that way live a long time. My 99 is bone stock, kicks but, and has never needed rebuilt. Good luck

I agree that Doo worked out the bugs with the '99 DPM, and it is the better of the two. ('98vs'99) BUT.....I have converted two x motors to std 670 ignition/no DPM with NO issues at all, and no appreciable decrease in performance. Although the X/HO CDI module apparently has a different advance curve programmed into it, I doubt that the average guy is going to have his sled in such a fine state of tune that he would ever notice the difference. Some of the X parts are getting pretty scarce these days, and if you cannot find the right parts, you have to do what you gotta do to get the sled running, right??

I have torn-down, ripped into, rebuilt, owned, and ridden MANY 670 sleds... summits, MXz's, X models, HO models.... piped, ported, stock and in between.... I'm just passing along info from my personal experience dealing with these sleds. My suggestion to run the standard 670 ignition system stems from my own problems with DPM "bugs" that just could not be figured out. If he has the stock 670 ignition system already, that is a much cheaper route than trying to find a bunch of used parts, or very expensive new parts that may not even be available anymore. The '98 DPM was available one year. The '99 DPM was available one year as well. Regular ol' 670 ignition systems were around for at least 6 or 7 years, covering several different sled models using the 670 engine. A much cheaper and easier to find alternative to somebody on a budget....

yup

What zachmandu says is true.....and works.