Hard to Start Hot Engine XS650SH

Paul Sutton

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I wonder if some one can point me in the right direction. My SH starts easily from cold using the choke on the 1st stop (BS34) and throttle fully closed, even at 0 Celsius. Usually only takes 2 or 3 kicks maximum. The bike pulls well through all gears without any missing or splutter and no backfire when going down hill with throttle closed.

When the engine is heated up after riding for say 30 minutes or more I find it reluctant to start either by kicking or using the electric starter unless I open the throttle slightly. I have checked the plugs and they look good without being too rich or lean - light grey in colour.

Once the engine is restarted it then runs without fault. The issue is restarting when engine is hot.

Thank you for any thoughts you share.
 
Jim, I only need to open the throttle very slightly to restart when hot and the restart is very easy i.e. 1st kick. I have spotted a comment by DogBunny in the following 2016 thread where in Entry 7 he says this is normal:

http://www.xs650.com/threads/81-han...-hot-need-a-plan-of-attack.45769/#post-458001

It may be that this is more noticeable in Winter because it was not happening back in Spring and Summer??
 
I'm being a bit cheeky here... but we've had electronic fuel and ignition systems for so long now that I think people forget what it was like in the "old days" of carbs...
We've grown used to just turning a key or pushing a button and letting the computer sort it all out.
My opinion Paul, if that's your only complaint... you're a lucky man:)
 
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Thanks for Jim, I have been out of riding for 30 odd years but I do not recall this issue before. I will just go with your's and DogBunny's comments.

I am a lucky man!!!
 
Yes, on hot starts, cracking the throttle open a hair is normal, at least on my '78. Cold starts with choke are no throttle until the motor catches, then I feed little blips into it to keep it going and bring the R.P.M.s up, sort of nurse it into running, lol.
 
Yes, on hot starts, cracking the throttle open a hair is normal, at least on my '78. Cold starts with choke are no throttle until the motor catches, then I feed little blips into it to keep it going and bring the R.P.M.s up, sort of nurse it into running, lol.

That sounds exactly like my start up routine.
 
I am thinking hard but do not recall doing this on my 1B all those years ago. Thanks for the conformations on this being normal. I shall sleep peacefully tonight once I have watched Gene Hackman in Heist.
 
Yup - me too. I think that Jim’s comment is right on.

Today’s vehicles have closed loop digital engine management and fuel injection systems that measure a bunch of parameters and then adjust everything from mixture to spark timing to throttle position literally hundreds or thousands of times per engine cycle. That looks after a multitude of sins ranging from cold crappy weather to bad fuel to changes in altitude to engine wear including poor compression and dirty spark plugs - and it has spoiled us.

I give a lot of public talks about automotive technology and I often ask a crowd “please raise your hand if your car has failed to start this week...this month...this year...in the last 5 years?

It is a very rare thing for anyone’s hand to go up - and then I ask the older folks to cast their minds back to the 1960-70s timeframe. Every (grey haired) head in the room nods knowingly. Our bikes have that same 1970s open loop, primitive technology carburation and ignition systems (for the most part) and that is why they run as they do.

Pete
 
Indeed! The last bike I had that had points in it was the Norton 850. I didn't have it long enough to get some sort of ignition upgrade. Amal weren't exactly high tech carbs . I noticed late '79-'80 most mid to large cycles got the E-Ignition.
 
My 2007 ST1300 has 73000 km (around 44,000 miles) on it and it’s a decade old. It runs EXACTLY the same every single time I start it. My XS650 runs a little different from one day to the next.
 
No, I reshimmed it a time or two. It's just part of owning one.
 
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Every one of my OLD bikes has its own starting procedure and cold starting is different than warmed up starting. I really don't notice the differences, they're automatic.

I know you're kick starting, but dirty, worn starters work better cold than warm/hot.

Scott
 
If you're looking for work suspect slightly weepy float valves or leaking float valve o-rings. eith will put a bit of a flood in it. But vacuum petcocks keep it from getting out of hand. Anyone remember the mistake of touching the throttle on a 60's V8 on a start 15 to 30 minutes after it last ran? The carb had cooled enough that opening the throttle set the choke. You'd have to go out and stick something in the choke plate to wedge it open to clear the flood. A big flame thrower wasn't uncommon. The guy under the hood would be yelling "KEEP CRANKING!" to suck the flame in.
 
Anyone remember the mistake of touching the throttle on a 60's V8 on a start 15 to 30 minutes after it last ran? The carb had cooled enough that opening the throttle set the choke.
Remember starting on a cold day and running back in the house? Two minutes later the engine would be screamin' away at 3 grand till you jumped in and tapped the gas pedal.
How far we've come...
 
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