KACR & Cold Starting
Member
1st Gear Member
Joined: May 2009
Posts: 69
From: Whidbey Island, WA
go cytocis, I bought the BMW to have an electric start bike to replace my '67 Triumph which was becoming hard for me to kick start. I wanted to continue having a vintage bike to stay active in my vintage bike club. The BMW was to only be a stop gap bike while my son was rebuilding the Aermacchi, but I've grown fond of the BMW and am having trouble convincing myself to sell it.
Norm
Norm
Last edited by BeenThere; Feb 1, 2012 at 08:21 PM.
Senior Member
1st Gear Member
Joined: Oct 2009
Posts: 262
From: Sonoran Desert, Arizona
@ Ranger: Thanks for the detailed questions. I don’t have the bike in front of me but I am reasonably confident in the below answers:
• What is the warm idle speed? - ~12-1300RPM
• What is the position of the throttle plate with the idle screw against the stop? – I have not taken a specific measurement per se, but at last check I recall the plate being just slightly open when returned against the idle speed screw stop.
• What idle jet are you using? – You mean pilot jet? Stock
• What is the idle mixture screw setting? ~2.25 turns out
• Do you have an aftermarket mixture screw? If so, what brand? - Stock
As mentioned, once started the bike runs beautifully. It warms quickly with choked idle at ~4000RPM (drilled starter at .019), then pulls well & revs stumble-free up to redline. I have a slight case of the ‘pops’ when shutting the throttle down at mid revs but nothing worrying.
Operation is unaffected by ambient temperature. I am currently riding in -10C to +5C temperatures but unless I use the primer, cold starting remains equally difficult regardless of -30C or +30C…
• What is the warm idle speed? - ~12-1300RPM
• What is the position of the throttle plate with the idle screw against the stop? – I have not taken a specific measurement per se, but at last check I recall the plate being just slightly open when returned against the idle speed screw stop.
• What idle jet are you using? – You mean pilot jet? Stock
• What is the idle mixture screw setting? ~2.25 turns out
• Do you have an aftermarket mixture screw? If so, what brand? - Stock
As mentioned, once started the bike runs beautifully. It warms quickly with choked idle at ~4000RPM (drilled starter at .019), then pulls well & revs stumble-free up to redline. I have a slight case of the ‘pops’ when shutting the throttle down at mid revs but nothing worrying.
Operation is unaffected by ambient temperature. I am currently riding in -10C to +5C temperatures but unless I use the primer, cold starting remains equally difficult regardless of -30C or +30C…
Ron
Senior Member
1st Gear Member
Joined: May 2011
Posts: 104
My 2009 SF won't start if it's been sitting for any length of time. I have a slip-on and a DJ kit installed. Here is what works for me:
Running it out of gas seems to work. I need more testing on that.
I've drained the carb bowl and the tank and used fresh gas, that worked.
More recently, if it's been sitting and won't start, I remove the seat and blast the air filter with starting fluid while cranking it. Works like a charm.
I'll see if running it dry will reliably make it start. If not, I'll either install a primer bulb or route a hose into the airbox that I can spray starting fluid into without removing the seat.
Running it out of gas seems to work. I need more testing on that.
I've drained the carb bowl and the tank and used fresh gas, that worked.
More recently, if it's been sitting and won't start, I remove the seat and blast the air filter with starting fluid while cranking it. Works like a charm.
I'll see if running it dry will reliably make it start. If not, I'll either install a primer bulb or route a hose into the airbox that I can spray starting fluid into without removing the seat.
Senior Member
Joined: Mar 2008
Posts: 3,406
From: N. Illinois
1st Gear Member
Starting fluid is bad for you engine (so I've been told ) BUT that's exactly how i used to start my old KLR 250. I had a hole drilled in the side of the airbox past the air filter. I had a rubber plug that I could remove from that hole and spray starting fluid in. Always worked great, probably horrible for the engine. I did all that before I knew any better.
It works, but don't do it.
Dan
It works, but don't do it.
Dan
Senior Member
Joined: Sep 2009
Posts: 5,050
From: Abilene, TX
1st Gear Member
Starting fluid is bad for you engine (so I've been told ) BUT that's exactly how i used to start my old KLR 250. I had a hole drilled in the side of the airbox past the air filter. I had a rubber plug that I could remove from that hole and spray starting fluid in. Always worked great, probably horrible for the engine. I did all that before I knew any better.
It works, but don't do it.
Dan
It works, but don't do it.
Dan
Senior Member
1st Gear Member
Joined: Sep 2011
Posts: 379
From: Detroit, MI
Idk I popped a rod in my buddies old chevy s-10 with starting fluid, it does cause an aggressive burn on ignition, but it had the death knock for a bit so I wouldn't go as far as to say it was the starting fluids fault... In small engines its not preferred because its a dry start, especially for 2-strokes; which is why I use penetrating oil in place of starting fluid on all my small engines now. Can't say if this is a good idea for my SF though.
Last edited by LikesToThump; Feb 4, 2012 at 09:21 PM.
Thread Starter
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Senior Member
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Joined: Mar 2011
Posts: 695
So it appears that TNC was on to something when recommending a compression check. *I obtained a set of small engine adaptors for my gauge, plugged it in (albeit cold) and got a reading of 70psi! *Far lower than one would expect an engine to fire at...
Given that the engine runs beautifully once fired up, doesn't smoke, has valve clearances that are within tolerance, and exhibits none of the normal poor performance characteristics of an engine with low compression (it'll run 136kph), it's gotta be the KACR.
My work schedule & wife limit my 'zen' time in the garage so I am not sure when I might get the valve cover back off to check the KACR for binding (as jworth94 found to be the source of his cold kickstarting issue), but I am now intrigued by another arrow which appears to be pointing at the KARC as the source of cold staring hesitation. Perhaps the KARC's centrifugal weights are operating correctly but causing the exhaust valve to open too much(?).
Typographical errors by*iPhone
Given that the engine runs beautifully once fired up, doesn't smoke, has valve clearances that are within tolerance, and exhibits none of the normal poor performance characteristics of an engine with low compression (it'll run 136kph), it's gotta be the KACR.
My work schedule & wife limit my 'zen' time in the garage so I am not sure when I might get the valve cover back off to check the KACR for binding (as jworth94 found to be the source of his cold kickstarting issue), but I am now intrigued by another arrow which appears to be pointing at the KARC as the source of cold staring hesitation. Perhaps the KARC's centrifugal weights are operating correctly but causing the exhaust valve to open too much(?).
Typographical errors by*iPhone