Ported intake? see pictures

[Bob Vehring]

If its not the plungers my usual first stop on idle rich is to see the needle and seat, Phil covered most of the rest

[YAMMIEGOD 3:16]

THIS IS WHEN YAMAHA DRIVES YA TO DRINK. MY 83 AS STOCK 8U9 CARBS. NO NEEDLES ON CHOKES. 3:16 (yammie tony)

[Bob Vehring]

I'll drink to that

[opsled]

THIS IS WHEN YAMAHA DRIVES YA TO DRINK. MY 83 AS STOCK 8U9 CARBS. NO NEEDLES ON CHOKES. 3:16 (yammie tony)

Ya, and the parts book shows an 8U9 part # for all the plungers on all the years and even on all the EX570's with 38 Mics. I didn't look at the end of the part # though. It could have had a -01 in there that would have indicated a change. Like the inner chaincase on the Vmax-4. Same part with one change for the 800's.

Ruined my 51 year perfect record for perfection. (lol)

opsled

[VMAXMARK]

THIS IS WHEN YAMAHA DRIVES YA TO DRINK. MY 83 AS STOCK 8U9 CARBS. NO NEEDLES ON CHOKES. 3:16 (yammie tony)

Ha! That may be my problem - I'm usually drinking when I'm working on it!

My sled has a primer installed on it so maybe I should just use that instead of the enrichener/choke? Just leave the plunger springs real loose so I know they are fully seated in the bore.

I havn't had time to fire it up since cleaning the carbs but I will tonight or tomorrow and see what happens.

Should I be running a little pre-mix in the tank since the ports have been modified somewhat?

[tyler440]

i would say no... a little smoothing of the intake, isnt going to change how much oil your crank bearings and piston rings need

[vmax-540]

What makes this even more difficult to figure out is these are old sleds and who knows over the years the plungers could had been dropped and lost and were replaced with what ever they could get at the time. VMaxmark did you check when you had the carbs apart to see if maybe someone had replaced any of the jets with different ones, I have seen people put all sort of jets in thinking it would do all sort of things. I would start with the original jet specs, and make sure the carbs are synced real good and see what that does.If it still runs fat and you can't find any reason for it to not run clean then try adjusting your pilot screws, set you idle at about 3000 rpm's and start turning both pilot screws out a 1/4 turn at a time until you get the highest idle speed, if you have turned them out more then 2 turns then replace your pilot jet with a one size smaller one and start over to see what that does. Most of the time you should end up with anywhere between a # 35 or # 40 pilot. Don't forget one important thing sometimes a good BLAST down the road will do wonders as well. Hope this helps ya..

[Bob Vehring]

I've posted this before, IMO people tend to give the pilot and the maim more credit then they deserve. At anything other then idle or WFO the needle and tube does most of the metering, determining if your rich or lean.Their relationship is also the hardest to understand because it constantly changes with slide position. We might also remember that today's gas is nothing like the gas available in the 80's. The amount of alky today can throw the old recommendations right out the pipe.

I've also posted before, my thoughts on reading plugs and pistons to gauge jetting. In racing or at least most racing, your either wide open, or off the gas. Thats what the color will show you, Remember most racers would carry a wrench with them so they could cut the power at the end of blast and check it before even driving back to the trailer. They saw the color of running wide open, and nothing else. On a trail sled 99% of your driving is a mix of different RPM, load,and throttle position. Whatever color or pattern you see is going to be a view of all of that, not necessarily what is happening at WOT. Also worth remembering, back in the 80's we had pretty basic Petro based oil and real gas. Today, even non syn based oils are made from much better bases and are cleaner and unless you run race gas or have non ethenal fuel available the Alky in their is basically a solvent Medium tan then is different from medium tan today.

[VMAXMARK]

Well I fired it up for the first time since cleaning the carbs and it was nearly a disaster. It started fine and actually idled nicley for a bit but then suddenly the rpms kept rising on there own until the sled took off and out the garage- unfortunatly the door was closed and it wacked it. I was able to catch it before it picked up too much steam so no damage. Good thing the door was closed or I might been chasing my sled around the neighborhood. Lesson learned I raised the track on the lift before trying again and it did the same thing. Apparantly one or both carb slides were hung up and not closing.

I took the carbs off again and reinstalled the slides with carbs in hand so I could make sure they were working right before putting them back on.

I fired it up again and it started easily with one pump of the primer, stumbled a bit while the bowls filled and then settled to a nice 1500 rpm idle. I thought cool- it's fixed but alas I was wrong again. I flipped the thottlle and same as before- bogs out and has to be feathered to get the rpms up and then it runs great.

The weird thing is after reving up the motor some times it will settle back down to a 1500 rpm idle and sometimes it stops at 3000 rpms. When it stops at 3000 and I flip the throttle there is no bog or hesitation and responds nice and crisp.

At that point I notice the choke flipper handle rod is sticking up and not returning on it's own and needs to pushed down. I decide to take the flipper handle off so I take a small screw driver and begin pushing the roll pin out and WHAM- the screw driver pops through the handle and embeds itself in my finger! Luckily the bone stopped it from going all the way through ; ) I pull the screwriver out and blood starts spurting like a primer bulb. Now I dont if it was the blood loss or the pain but I got dizzy and had to sit down for a while. After that I decided to call it a day.

[VMAXMARK]

Here is a video I took before I impaled my finger. I ended up going to the doctor the next day because my finger was turning funky colors and feeling numb. The doctor said it was a good thing I came in because it was infected and I actually broke the bone in the tip of my finger. A splint, pain killers and antibiotics and all is well.


http://s151.photobucket.com/albums/s152 ... H05422.mp4

[chrisrider63]

When you have it running on the stand spray gas from a torch or ether on the clutch side seal if the rpms increase then you have a crank seal issue also check wires and the main wiring harness disconnect and spray cleaner on the connections.

[Speednutt]

I have seen primers go bad on Doo's that allowed the fuel to flow thru the plunger while running. I would say to disconnect the plunger and see if that fixes your issue. When your sled is idling and at low rpm that is when there is the greatest amount of vacuum in front of the carb slide.