Should it be this hard to start?

R

Reeve

New member
I always figured it was normal to have to pull it 8-12 times to get it to fire after sitting for a couple months. Then I got my self another sled and it fires up in 2-3 pulls after sitting the same amount of time. My Vmax is a stock 93 jetted for 5000 ft altitude where I ride. My other sled is a 96 Mach Z 780 jetted for the same altitude. My Vmax starts first pull when warm and on 2-3 pulls from dead cold after sitting a day or two. If it sits a few weeks my shoulder takes a beating to get it to start. Where should I look I To cure this problem?
 

First check and see if the choke is on all the way.It could have to much free play in choke cable and only get a half choke when operated? Check this first.
 
My choke opens all the way and I still have to pull like crazy after sitting for a few months. After. It starts it 2-3 cold a 1 warm every time it's only when it sits for a long time.
 
Over the years, I have had some start super easy with only a few pulls after sitting and some take quite a bit of pulling. The best way I've found is to put a small amount of premixed fuel down each cylinder with fresh plugs for the first start. That seems to prime to system for me and after that it usually starts pretty easily.
 
I'm completely going through the carbs right now. They were a mess after sitting these last two snowless winters in the NW. This issue was just the same with clean carbs though. I have had two old Phazers that never took much to start and figured it was because they were small and easy to pull over. But now with my 780 Rotax starting so easy it's got me thinking there must be something up causing the 750 to be so hard. Only thing I can think of would be bowl gaskets allowing the fuel in the bowls to evaporate but I don't see any signs of fuel leaking from them. Might just replace them anyway. Anybody have a good source for bowl gaskets?
 
Maybe fuel evaporates out the vents. 4 vents compared to 2 on your twin. Replace the needle/seat o-rings. These get brittle and and let fuel drain into crankcase. I've never seen a problem with bowl gaskets but Yamaha dealer or local parts store can get them.
 
I prime mine every year. I pull the 'boost bottles' and dump a little in each and it usually starts up in a couple pulls and runs. All season after that it will start in 2 or 3 with the choke full on.
 
Ok so I got my carbs all cleaned out. Only thing I didn't disassemble was the floats and chokes. I opened up the chokes and blasted carb cleaner and then compressed air through them. They all seemed to flow just fine so I called it good. I then did the same with the floats. I didn't want to try to tap out the float pins because I broke a float tower when I did that on my 38mm flat slides on my 780. Next cleaning I'll make a custom tool to press out the pin while supporting the tower but I didn't have time this go round. Everything looks good. Only question I have is the pilot screws? The stainless steel needles. I checked a couple before I took them out and they were 1.5 turns out. I assumed they would all be the same so I pulled them all then read in the manual each was factory set. I just pulled the needle spring and washer under the spring. I didn't dig any further. What else is under there? Anything to check? How do I adjust the pilot screw if I don't know where exactly it was set?
 
You really need to pull the floats and check the rubber oring on the needle and seat. Those go bad and create lots of problems. Like fuel draing out of the carbs into the crankcase. I use a punch and tap it with the butt end of a screwdriver to remove the float pin. To reassemble I use needlenose pliers and gently squeeze. The screws you can set from 1.5 to 2 turns out. I've tried both and in between on several sleds and never noticed a difference. Go with 2 turns out. There is the needle screw, a small washer, and a small rubber oring in there.
 
Ted thanks for the tips. I'm just scared because I did exactly that on my 38mm flat slides on my 780 and it broke a tower off one. Luckily I know a very talented tig welder and he and he was able to fix it. I didn't have any problems with the seats so I'll take my chances this time. I am a machinist so next time I pull the carbs I'll design a little tool to support the tower and push the pin out. Maybe I'll make a small batch to sell for a couple bucks if people are interested. I would like to replace those parts but have to get the sled running in the next couple days for a quick shake down run. I'll set the screws two turns out like you said. What exactly do they do? How will I know if they need adjustment?
 
Screws on the bottom of the carbs on the Yamaha flatslides are "Fuel Screws" and they control the fuel primarily at idle and up to 1/8 throttle. Opening the fuel screws adds fuel or richens the mixture and closing them leans the mixture. If they are too lean the sled will idle high and hesitate when the throttle is opened if they are too rich the sled will bog and run poorly at low speed. The fuel screws effect the mixture somewhat throughout the throttle range although less as you move towards full throttle. Fuel screws also effect fuel mileage if they are too rich. On a stock VMAX 4 I like them open 1 1/2 to 1 3/4 turns.

When cleaning the carbs I too recommend removing the needle and seat as there are small "Top Hat" shaped fuel screens under the seat that can plug and create havoc, like unexplained melt downs ect. Most people don't even know these screens are there....I have removed them on all my VMAX4s, SX triples, and SRXs so I don't have to worry about them clogging.

JM.02c
 
Thanks for all the tips. I got the sled up and running and after quite a bit of running on three it cleared up and started running good. Not sure why it was taking so long to fire that one cylinder. I took it for a quick spin and checked the plugs. They all looked good. I think I'm going to pull the carbs one more time and change the float needles. I need to pull the air boxes anyway because I replaced the fuel lines and they must have been a bit thinner because the clamps aren't really tight. Going to get smaller clamps and maybe replace a few more lines under there. My last local Yamaha dealer shut down years ago. I think I'll also replace the bowl gaskets at the same time. Anybody have part numbers and a good place to buy online? It was great to get the Vmax back on the snow after missing the last two seasons due to lack of snow. As usual I took it in snow that was far too deep and soft to support the girth of the Vmax. I sunk it once and had a hell of a time turning it around on a trail freshly blazed by a couple of 163 sleds but it did well considering the 5 feet of soft snow!
 
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