Hard to start when cold.

[Bullwinkle58]

07, 400s, clarke tank, manual petcock, jd jetting needle & pilot, 3x3 mod, de-smogged, only 1300 miles on the odometer, runs great.

The only problem I have is when its cold, I have to crank & crank & crank & blip the throttle (with the choke on), and eventually it will start chugging, then it will idle like normal & fire right up the rest of the day. Its just that first cold start after its been sitting for a week or two, as if there is no gas in the carb. Even after sitting overnight it will start right up.

Any known issues that cause this, or ideas of things I should check?

[GaSmoker81]

sounds pretty normal for a dirt bike. even though my drz fires up everytime. for soem reason it doesn't like the choke though. mine fires up better with choke off.

my honda crf450x would act like that if i dint crank it once a week.

Edited April 17, 2012 by GaDRZ400sMan

[Noble]

Drain the gas out of the carb when you park it. You can put a short hose on the drain nipple, and there is a convenient drain screw. Just drain the carb when you park it. When ready to start it, turn the gas on, wait about 30 seconds for the carb to refill, should start right up. Works for me.

[Bullwinkle58]

I actually just turn the petcock off, start the bike & run the level in the bowl down before I park it, but its hard to start leaving fuel in the bowl also. I'll try without the choke next time. This is my first electric start bike & i'm kinda paranoid about burning up the starter. Glad to hear its pretty much normal though. Thanks guys.

[Noble]

Not normal for me. I always need the choke cold. Starts in less than 2 seconds with fresh gas in the carb.

Running the carb out of fuel leaves a lot of gas in the carb still.

My procedure is - turn off the gas (manual petcock), drain the gas, pull the choke, key on, hit the start button, it will run about 1/2 second, key off, park it.

[Bullwinkle58]

Got it...thanks Noble, i'll try that.

[daveyedgar]

Not normal for me. I always need the choke cold. Starts in less than 2 seconds with fresh gas in the carb.

Running the carb out of fuel leaves a lot of gas in the carb still.

My procedure is - turn off the gas (manual petcock), drain the gas, pull the choke, key on, hit the start button, it will run about 1/2 second, key off, park it.

 

this worked for me, but i'm curious, why does it work? what happens to gas left in the carb overnight?

 

my battery is fairly new but on cool mornings(as in 60*F in florida) sometimes it seems like the engine locks, like it will crank once or twice and stop as if something is blocking it.

Edited November 12, 2013 by daveyedgar

[Craigo]

 

 

my battery is fairly new but on cool mornings(as in 60*F in florida) sometimes it seems like the engine locks, like it will crank once or twice and stop as if something is blocking it.

 

the introduction of fuel into the cylinder improves the ring seal ,  fuel volume as well does same.....and thus increases the cranking compression...

Edited November 13, 2013 by Craigo 485sm

[daveyedgar]

this wouldn't be a symptom of any problems with the auto decompression would it?

[eyeopenher]

same motor different toy... i have a 2005 z400... i never use the choke... starts right up...sitting a month or sitting a day... i shut off the petcock and run it out of gas before i shut her down... i keep a battery tender on her so the battery is always fresh and strong... 

 

my friend has a 2008 z400 yoshi edition... he has to crank the snot out of her no matter what.. no choke, no start for his. even in the dead of summer..... he has to choke his till its been run for at least a half hour...  now he forgets to shut off his petcock and never runs her till she eats up all the gas... but like i said. his is this way for at least a half hour.. if she stalls before she is warm, you have to keep the choke on otherwise its a no go...  

 

fresh gas, old gas. all the same on both bikes... not saying old gas is ok, but just saying what i have experienced... 

[john ryals]

 check valve clearance ,is choke working correctly ,jetting ??,I have a o7, never a problem starting ,3x3 done and jetted, air filter clean?  never blip throttle when trying to start, turn gas on, pull choke out fully  , hit start button, bike should start up , after a minute put choke to 1/2 till engine warm, push choke off after warm, go ride, sounds like you have plugged piolet  jet, choke circut not working correctly , valve clearances too tight..

[ohgood]

this wouldn't be a symptom of any problems with the auto decompression would it?

 

 

no. more than likely the fuel is gumming, or the pilot circuit is partially clogged, or the choke isn't working. 

 

when the auto decomp gets loose on the cam it gets NOISY. if it looses pieces, it gets CRUNCHY. 

 

i'd say clean the carb and look for trash in it. 

[daveyedgar]

thanks all,

 

I cleaned/rebuilt/jetted (3x3) the carb last february - been using non-ethenal gas ever since with the occasional sea foam.

 - how often you pull the carb for servicing?

 

the choke seems to work, takes much longer to cold start without it. When bike is warm and i pull the choke it stalls - indicating its working yes?

 

at 75*F it starts fine, and during the summer at 80*F+ it starts on the first or second crank.

 

glad to hear its not the decomp ?

 

checked valve clearance last april

ExLeft: between .254 - .279
InLeft: between .178 - .203
ExRight: between .203 - .229
InRight: between .127 - .152

 

wait... when valves wear do they get tighter or looser? tighter right? if so i'll check 'em this w/e.

I change my oil often (btw 500-700 miles 90%street) and use silkolene or equivilant.

 

I have a spare pilot jet i can swap out to see if that improves it.

[quick221680]

Had the same problem. I removed the auto decompression valve and I like the way it starts much better now. Plus one less thing to go wrong.

[Bluelunatic]

Not normal for me. I always need the choke cold. Starts in less than 2 seconds with fresh gas in the carb.

Running the carb out of fuel leaves a lot of gas in the carb still.

My procedure is - turn off the gas (manual petcock), drain the gas, pull the choke, key on, hit the start button, it will run about 1/2 second, key off, park it.

 

Thanks Noble. A very good suggestion!

 

I've noticed the gas turns an orange color when it has been in the carb for a few days/weeks. I plan to drain mine as soon as I get home. I always have hard start issues. When I had a bad FlexJet and idle setting issues, the only way I could electronically start the bike was after draining the carb and whacking the throttle full open. I always wondered why that was.

[daveyedgar]

sounds like we have the same problem

 

my bike does start up when cold in the first 1 or 2 cranks using noble's technique, so i'm not sure that my carb is dirty - if it was it would be hard to start hot or cold yes?

[Bluelunatic]

sounds like we have the same problem

 

my bike does start up when cold in the first 1 or 2 cranks using noble's technique, so i'm not sure that my carb is dirty - if it was it would be hard to start hot or cold yes?

 

I have a 434 rebuilt by Eddie with a FCR 39mm carb, 3x3, manual petcock, and R&D FlexJet. I went for a ride on Sunday and the bike had been sitting for 6 weeks or so. I don't need the choke here in California and its garage kept, but it took several minutes for me to get it to turn over. What Craigo said about getting fresh fuel in to seal makes sense now. I don't understand it, but I used to have to drain the carb to get a start even if I only had the bike shut off for 2min. That's no longer an issue after fixing my FlexJet (put the Keihin o-ring, washer, spring on it). I do typically hold the throttle wide open in order to get the bike to start if it refuses to fire after several tries. It hits that high compression and dies. So I shut it off, turn it back on, and just hit the strater and it comes on normally. Once I've been riding, even after stopping for lunch, it fires right up.

 

I'm going with an iridium plug the next time I take my tank off. It's sitting on the shelf waiting to go in. I also think Noble's trick will help immensely.

[mebgardner]

Same problem for me: Hard start at cold, and requires Wide Open Throttle (WOT) during starting with no choke. Idles fine after warms up for a few minutes, and then for the rest of the day starts on 2nd motor spin (ie: easily), and idles and runs fine.

 

If choke applied during starting, then seems to flood (smell of gas pretty strong).

 

2007 DRZ400-S, 8800 miles, OEM pipe, no 3x3, new OEM carb, OEM fuel petcock, 2700 ft altitude, 70-80 deg. daytime temp.,

 

I seem to read that valve lash adjustment is associated with warm start problem, not cold start, so I "back burnered" the valve check, which checked OK at 2400 miles.

 

New plug applied, no problems noted on the old plug, and checked it's gap clearance on both, which was good.

 

Air filter cleaned and lubed (more on this later).

 

I maintain a fuel filter in-line in the tank-to-carb gas line. Checks good for fuel flow.

 

No gas in the oil, the petcock does not leak. Checks good.

 

The new carb is because I rebuilt the original carb three times, and it continually had problem that would not solve (not this problem I'm discussing now). I replaced it and it was in good tune for many months, would start the cycle on the 2nd spin of the motor at any temperature, would fire right up, and idle and run fine at all throttle settings. ie: This is a new problem for me, not associated with the replacement OEM (Mikuni) carb.

 

I tried Noble's procedure (above), but when I attempted to drain the carb of gas, it would not stop flowing from the tank. The reason is, there's no manual shutoff. So, the fuel system acts like it's being siphoned out the drain hole when I open the drain screw. The flow of gas from the drain hole "pulls" fuel through the OEM petcock shutoff, and then from the tank.

 

So, I can not use Noble's procedure, as I can not stop the gas flow from the tank without a manual shutoff.

 

I read about how the WOT allows more air in during the startup. So, I figure I'm starting "rich", and that's why the addition of choke floods the motor.

 

I begin to look at the maintenance (or lack of it) changes, from the time when starting and running fine to "requires WOT during hard start."

 

I noticed there was an air filter cleaning in the time period.

 

I followed the filter cleaning directions when I did it, and I used Uni product per the directions (the "right" stuff). But I begin to suspect that's why I need more air to start it, too much oil?

 

I had a new, un-oiled, air filter on the shelf and installed it.

 

Voila! fires right up, no throttle applied. Acts just like before I had this new problem.

 

OK, remove it, and lightly oil the filter and re-install.

 

I think I'm on to something here, possibly another reason for "hard start on cold".

 

I'll get back to you when I get a bit more "stick time" on this fix.

Edited October 1, 2016 by mebgardner

[mebgardner]

So, I did solve this issue by allowing more air through the air filter. I had inadvertently sprayed too much oil onto the air filter after cleaning it. Then, starting the motor with WOT, and no choke, allowed enough air to get it running.

 

So, I will no longer follow the Uni oil can instructions: Saturate the filter, both sides, let stand 5 minutes, wring out excess.

 

This apparently puts too much oil into it, and blocks air flow at small motor flow (at startup), when cold.

 

With a new Uni air filter, and lightly sprayed with oil, my cycle now starts with no throttle input, no choke, and on the 2nd spin.

 

It was: Hit the magic button for  15-20 seconds, and apply WOT with no choke. Listen to motor spin and spin, eventually (at about 10-15 seconds) would begin to "catch" and fire, and be running at 15-20 seconds.

 

Now, its: Hit the magic button for a couple seconds, no throttle, and no choke, and its running in 2-4 seconds.

 

I've tried this after the cycle sat for a week, not carburetor drained.

 

My cycle now starts just like it used to, so I think its sorted out.

[mebgardner]

I'm at 12,500 miles now and my cycle became hard to start when cold, again.

It idles fine, and runs fine when warmed up, and this fall I cold routinely start it up with 1/2 choke and a couple seconds of the starter motor while at 3000 ft., and 75 deg. F.

Then, the first cold snap with the cycle in the unheated garage. Aaaaand it would crank and crank, sputter to life and die.

Nothing with choke or throttle would get the beast to start normally.

I re-read this thread, and knew the "too much filter oil" was not the problem this time. I also re-read the common advice of "valve lash out of spec" under these conditions.

I last checked my valve lash clearance at 2400 miles, and my notes indicate the exhaust valves were close to tight at that time (.009 and .009).

4 years later, and time to check the valve lash clearance again now.

Both Intake were at 0.006 in. (mid range), but both Exhaust were now at 0.008 (limit at "tight" end of spec.). Well, I'm looking for "out of spec", and I figure this is close enough.

I mark the timing chain with dabs of paint at 2 points on each cam, at the link pointing at the numbered arrows. Loosen the MCCT, and off comes the exhaust cam cover. I hang the chain with twist ties onto the frame, insuring it does not jump teeth at the crank or the intake cam.

I re-shim both exhaust to 0.011 in. (shims changed: 308mm -> 300mm, and 305mm -> 300mm) , and close it back up.

3-Bond sealant on the reused valve cover gasket to seal it around the half moons.

Spark plug looked fine, and gap is OK. I reuse that too.

Reset the MCCT.

So, I let the 3-Bond set up overnite, and start it up in the morning.

It's about 40 def. F when I pull it out of the garage, cool but not really cold.

Full choke for that temperature, and 2 seconds of starter button and the cycle turns right over and runs fine.

Warm it up, and fine tune the MCCT.

I'm out a whole $15.00 for the two new shims, and a bit of 3-Bond (which I had on hand). Yeah, I could have bought a shim kit, but not this time.

I put this episode down to "too tight valve clearance".

Edited December 28, 2017 by mebgardner