DiTech starting/stalling problems

[BuzzScooter]

I've got a 2002 SR50 ditech, derestricted and with a new pipe, roller weights and clutch spring. It's been running very well, except that when the engine is cold, it takes a lot of cranking to get it started and will eventually stall if I don't twist the throttle a little. Once it's warmed up a bit, it starts right away and doesn't seem to stall.

I had the start problem even before I put the new pipe on, and my dealer replaced the fuel pump thinking that it was malfunctioning and making it hard to start, but even after the pump was replaced, the problem persists.

I like in northern California, so it gets chilly, but not below freezing. I tried warming the bike with a portable heater for 15 minutes before I ride, and it seems to help a little.

Any ideas? Keeping the throttle open at traffic lights to prevent stalls makes people think I'm trying to race them, but I don't care about that. I'm mostly worried that I'm going to wear down the battery with all the cranking and / or someday it just won't start.

[beeper]

I'm in northern California also and I have the same problem although with an unmodified scarabeo di-tech. The problem started for me about a month after I bought it.

[laz224]

yes i had the same problem with my yamaha Aerox in colder weather what it is that you have to put a little paper by your air filter intake so it dosnt suck that much air and then itwill start better...it may work but if not then its something else..

[boyo3310]

my ditech duz exactly the same, i have a race pipe but its dun it all the time ive had the bike, takes 2 or 3 cranks wen its stone cold but is usually ok wen its been runnin a while.

[BuzzScooter]

I got the use and maintenance manual from one of the Aprilia websites and it says to never crank for more than 5 seconds at a time and that you should wait 10 seconds. It also says to make sure that the headlights are off or in the dim position. The dimmer setting doesn't seem to make a difference for me.

On the next page, there's a section titled "Starting with cold engine". It says that if it doesn't start on the first 5 second crank attempt that you can "rotate the throttle grip moderately." It also says "If the idling is unstable, twist the throttle grip slightly and frequently."

I'm already twisting the throttle while idling to keep it from stalling, but I'll try waiting 10 seconds and then twisting the throttle while starting. Although not too many people have replied to this thread, I guess it's a pretty common issue if it's mentioned in the manual.

[foxster]

I have posted about this before. There is a valve on the fuel tank that is vacuum operated. Which means under low vacuum it closes, it is spring loaded also so this is the problem. When you start the scooter it doesn't create enough vacuum at times to open this valve and feed fuel to the injector. I take the vacuum line off and cut it and put an inline vacuum check valve or "one way" valve. Problem solved forever. It is amazing how many road bikes have this same valve on them. It is a shut-off valve for idiots. Not to say that you people are idiots, but it's there to shut the fuel off when the engine is off so the fuel doesn't fill the engine. :smokin:

[JIMMC15]

I bought 2 Ditech's. One has run 900 miles without any problems. The second one stalled and wouldn't start when I got it home. Cleaned the plug and it would start but occasionally stall at a stop. I got used to cracking the trottle when stopped so it wouldn't stall. Finally took it to the dealer last month after 150 miles to have them look at it. They said the Air filter in the Ditech is "Oil Charged" like a K&N filter. It had too much oil in it from the factory. They said it was restricting the air and fouling the plug. They cleaned the filter and replaced the plug (I had already replaced the plug once but it didn't seem to help) I was sceptical but it's run great ever since I got it back. Clean the air filter, it may help!

[BuzzScooter]

Foxster, can you give us a little more info on how you solved your problem with the vacuum valve? Maybe a short description of where you cut the line and what you removed. I'd really like to fix this problem and if it's that easy I'll be really happy.

JIMMC15 - thanks for the tip. I'll check the air filter too. I've got the SR50 maintenance manual, so I know how to do that.

[Deviltech]

the ditechwill not start right away if it has been sitting. the system works on pressurised air over the fuel pressure. it takes a few cranks before the air pressure is up to make it rich enough to run.
i have had a problem with a ditech that fouled plugs and found it to be a bad air injector causing a rich mix to do in the plugs. it takes a while if you ride full throttle all the time but stop and go does it faster.
as far as cold goes i take mine out in the winter some times and i live in milwaukee(it sucks here)

[foxster]

There is a vacuum line, on the carb models it's on the very front of the CARB, on Ditech its in the manifold I believe. I only looked at a problem Ditech for a few minutes at the racetrack. But I cut the vacuumn line about 75-90mm from the engine(carb) or manifold. Then I put an INLINE oneway vacuum valve. Most motorcycles have this vacuum fuel shutoff valve, I don't know exactly why, but its because some people can't shut off the fuel petcock or that the bike doesn't have one. But this valve on the scooters is spring loaded and it takes vacuum to open it. If the reeds in the engine are "soft" as the stock ones are, it will not create enough vacuum to open the valve and thus no fuel. I have fixed this problem on Gilera DNA's and Aprilia SR50's and others including Yamaha's. What I recommend is to lightly rev the engine when stopped to keep the vacuum there. Vacuum is measured in negative inches of mercury but for those who don't understand that, just keep the throttle up more than idle or "blip" it when stopped.