Just picked up a vt600 from a friend, it sat for quite awhile then another buddy wanted to resurrect it so he changed the reeds and cleaned carbs then ran it. Ran terrible so he put stock size jets in it and it was better but when warm it would fall on its face, be rough like one cylinder went down, then come back into it. Lather, rinse, repeat. So he gave up, it sat last year, and because my friends all run cats or ski doos I decided I need it. It fired right up and ran with a jump pack and a shot of starting fluid, idles great, revs fine, but of course I can't really test drive it yet with no snow or frozen pond. They suspected the smart carb solenoids and I'm trying to find out about them but it seems to be a national secret and info is scarce. Will a dead or stuck solenoid cause this or is it a base carb problem? If it is a smart carb issue will regular old flat slides interchange easy enough or is that a whole other disaster?
Based on your description, I would venture to guess (pun intended), that you have a more underlying problem than the smart carb system. Info is scarce on that smart carb system because it was a limited build for a short time. However, it is a very simplistic system and not that hard to troubleshoot.
That being said, if your dropping a certain cylinder at a given temp, it may be the main solenoid valve on that particular carb. However, it could also be a dirty magneto, bad spark plug cap, corroded grounds, choke cable adjustment, etc. Your sled is equipped with a self diagnosis feature that should display a fault code if there are any issues with the associated parts with the smartcarbs. Is the self diagnosis function operational? You should see 3 quick flashes of the temp sensor when you fire the sled.
From there, you can ohm out most of the system's components, but some will require a special diagnostic coupler to activate. You will need a Yamaha dealer that has been established and would have the test lead on hand, or, if you want to go full on ghetto, you can fashion your own, but its a do at your own risk. I can somewhat guide you on that one.
As for eliminating the smart carb system, its a bit more involved than just swapping carbs as that cdi is specific to the system. I would think that in addition to the carb rack, you would need a wiring harness and cdi from a 97 600 twin model.
I have the troubleshoot info on hand, along with other pertinent info for that system. It's no national secret, you just need to find the old guys that have lived through it.
Old guys are usually the best guys.
I know there's 2 solenoids per carb, what exactly are they Doing? Regulating fuel Flow? Top or bottom the main? The guys that had this are decent auto techs but even so i'm going to start with the basics and work my way to it being an electronic problem. The diagnostic light doesn't flash when started, hoping that's just a bulb but I'll look into that. I did see some solenoid test leads on ebay, if I need to get one then so be it.
The solenoids alter/increase air flow by opening up passages in the carbs. The upper solenoids are the mains, and the lowers are the pilots. The main solenoids essentially control the pressure in the bowls. When they open, they create a negative pressure that leans out the air/fuel mixture.
The pilot solenoids open up an air passage associated with the pilot circuit that adds air to the mix and leans it out. Both sets can be tested with the test coupler and a 12v battery and listening for them to click. They are working if they are clicking consistently after a few minutes. Hence the need for the test lead as you wont hear them with the engine running. You can fashion your own with some simple wiring and knowing where to land the leads, but if the ebay ones are cheap and have the in-line fuse, you would be better off.
Hope for the best on the bulb. From there check your stator output along with the condensor wires and connections. I would have to look up the stator specs if you dont have them.
Got a little snow so I was able to rip it around the lot some, ran pretty good at first, did seem to be a little boggy around 20 MPh but would come out of it and pull nice up to 70 before I ran out of room, did that a few times, shut it off awhile, went to park it and a cylinder went down. Pulled a plug wire off at a time and the left sides wire has a spark leak near the plug, don't think that's the main problem but not helping. Put two new plugs in and was back to full power, I guess this was a constant thing for the last rider, he did put a new coil on. I'm going to swap the wires and see if the right side goes down or it stays on the left. Belt is trashed too so have a new one coming. It was pretty impressive for a 600 that weighs a ton, just need to keep it that way.
Check your plug caps for resistance and consider replacing them, or verifying a good connection on the wires. The low end bog could be associated with the fuel screws or a plugged air jet on the carbs. There is a tiny o-ring on the fuel screws that may be fatigued or missing.
You may also consider adjusting the oil cable as they do stretch over time and you could be over oiling. An over rich condition on your plug foul could be oil related.
I'm guessing the plug caps are cheap so I'll get those and definitely will check the oil adjustment. I did get the red light to come on and it flashes 3 times when started so the computer is happy right?
Good to hear on the self diagnosis system, yes, the computer is happy. Plug caps are cheap, around $5 for aftermarket. NGK TB05EM on that route, or you can go oem at over $20 8DG-82370-00-00.
Rule that out as an issue and then look back at the carbs.
I got new plug caps today and will be installing them tomorrow, I checked out the oil cable and it does pull just before the throttle moves, is that right or should they be even or throttle just before or? The other day it started on one pull, today nothing after like 20 pulls and I gave up.
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