Cranking a 2 vs. 4 cylinder bike

[kevdog3019]

In general is cranking a 2 cylinder Guzzi 750 easier than say a Jap 4 cylinder 750 or about equal?  Battery choices is why I need to know.
Thanks 

[oldbike54]

 No generally a 4 will easier to turn over than a twin .

  Dusty

[jabberwocky]

I'd say it's harder than a 4 cylinder. You are never pushing more than one cylinder through compression at a time, and a big cylinder compresses more air than a small one. Life with kickstart-only bikes teaches you this.

[LowRyter]

4 cyl should turn over easier. You have twice the chances of the spark catching

[lucky phil]

What takes more effort, the biggest bite of a hamburger you can take or a modest bite.
If you can figure that out you will have your answer.
Ciao

[oldbike54]

 There is also flywheel and reciprocating weight and mass to consider . Normally the combined weight of these components in a twin is heavier than in a four .   


  Dusty

Edit , fixed it Jim  :D

[Triple Jim]

There is also flywheel and reciprocating weight and mass to consider . Normally the combined weight of these components in a twin is heavier than in a twin . 

  Dusty

Huh, I would have thought the weight would be exactly the same.     

 :D

[oldbike54]

Huh, I would have thought the weight would be exactly the same.     

 :D

 No or very little flywheel in a 4 . Also , and I am NOT an engineer , but a piston weighing 3 Oz's takes less than half the connecting rod to control , which 6 Oz's , which allows the crank to be lighter still .

  Dusty

[steven c]

 Back when bikes had kick starters still on them a 750 would kick over almost like a 2 stroke.

[wrbix]

 Of course, consideration of a starter upgrade:
Motorrad Electrik markets a Mitsubishi planetary gear starter that reportedly spins faster at lower current draw - might be a direct drop in for the Lario. Let me know if you go that route. Interested to see how that goes.

[Triple Jim]

 No or very little flywheel in a 4 . Also , and I am NOT an engineer , but a piston weighing 3 Oz's takes less than half the connecting rod to control , which 6 Oz's , which allows the crank to be lighter still .

  Dusty

Dusty, go read your original post.   ;D

[oldbike54]

Dusty, go read your original post.   ;D

 Well duh  :-[ ;D Anyway ...

  Dusty

[oldbike54]

Back when bikes had kick starters still on them a 750 would kick over almost like a 2 stroke.

  Guessing you mean a 750 four .

  Dusty

[jacksonracingcomau]

Can't quote CCA cos I didn't measure it but I got a new Lithium battery from a friend's widow to try in my Guzzi
Wouldn't hardly turn it, let alone start
But would easily start my Brumby (Brat in US) 1800cc flat four ute
Since, I discovered it would start his 1200cc four cylinder Suzuki easily but not his 800cc triple Triumph that it was intended for, he'd replaced the original in that.
I gave it to another mutual friend to use in race bike

So, absolutely certain you need more CCA for a twin, exactly how many does depend on other things
Battery I use claims 280 CCA, I'm sure that would start the Lario

Search on here, others have fitted Lithium batteries to Guzzis with success, if they work on BB, SB should be a doddle

[lucky phil]

Can't quote CCA cos I didn't measure it but I got a new Lithium battery from a friend's widow to try in my Guzzi
Wouldn't hardly turn it, let alone start
But would easily start my Brumby (Brat in US) 1800cc flat four ute
Since, I discovered it would start his 1200cc four cylinder Suzuki easily but not his 800cc triple Triumph that it was intended for, he'd replaced the original in that.
I gave it to another mutual friend to use in race bike

So, absolutely certain you need more CCA for a twin, exactly how many does depend on other things
Battery I use claims 280 CCA, I'm sure that would start the Lario

Search on here, others have fitted Lithium batteries to Guzzis with success, if they work on BB, SB should be a doddle

What temps were you trying to start the guzzi at?
LI batteries are very cold temp sensative and sometimes Ducatis have the same issues with them. Usually turning on the headlights for a few minutes before cranking helps. Late LI batteries are probably better.
Ciao

[kevdog3019]

Thanks all. I've got a lithium Iron on it now for three years (Lario). I'm looking at something with only 4 cells (antigravity) that would tuck up nicely out of sight. I'm not certain I can get away with that since it says up to 600cc, though a guy cranked his Kawa 900 4 with it. That's why I asked. I have lightened bits in my Lario (flywheel/rods) but more compression. Hmmm..,
It claims 120 CCA the 8 cell 240cca. Guess I better not risk it. 240 will do it.

[dsrdave]

Fewer cylinders usually means tougher to crank.  Ever kick start a 500 single ???  If you're thinking about a lithium battery I used an 8 cell Ballistic battery for several years on my 850T and the OE Bosch starter and had no issues.  I suspect if you upgraded to a legit Valeo starter that would help also.

[jacksonracingcomau]

What temps were you trying to start the guzzi at?
LI batteries are very cold temp sensative and sometimes Ducatis have the same issues with them. Usually turning on the headlights for a few minutes before cranking helps. Late LI batteries are probably better.
Ciao

wasn't cold, as said easily started Brumby in same weather (maybe 20 C)
tried all warming tricks, even tried warm engine, wouldn't play
Was state of art comp controlled German battery, think you bought Wilbers from Greg, came from them, used in all their (4 cyl) racebikes, no go for triple or twin

Kev-- agree with safe 240, 120 doesn't sound nearly enough
But I've just ordered one of these jump start tiny batteries,
http://www.gadgetcity.com.au/quantum-battery-backup-charging-&-jumper-lead-power-pack-p-2905.html?cPath=94_207
will test it and report, not sure why not but they say not to leave connected to battery when running but you can charge it with cig lighter from running vehicle.
Otherwise one of these would be perfect cheap tiny battery !!!
Might be possible to connect big +ve lead to starter only, run lights ignition etc from alternator with just charging +ve wire going to this unit ?
Big -ve lead permanently earthed.
$69 test, I can afford that

[kevdog3019]

Please report on findings. I've got a pocket between my tank and frame that ID like to fill with a battery for my build. Small is good.
Thanks

[kevdog3019]

My bad, just realized I was looking at AG's AG401 specs NOT their XPS (Extreme Power Series). It will start vehicles up to 1300cc and works for V8 trucks. It says it will easily start a high compression Ducati V-twin. Ok... only catch is it has low capacity and is not meant for a "daily driver". However, reviews are from folks using them in 1300cc and 1100cc bikes as permanent drivers and they aren't complaining. So... I'm Safe from a pure starting standpoint but wondering from a capacity standpoint. This is not my touring bike and I take it out for good long spins in the twisties not in high traffic zones. I think it's worth a shot at just over $100 and if it fails I use it as a backup or toss it. Videos show quite impressive results of starting trucks, etc. over and over without hesitation. Boils down to capacity.

[Tobit]

Displacement being equal and not considering valve and ignition timing, I'd say a single or twin is more difficult to turn over than a four. 

I notice that some HD guys building hi-compression strokers put compression releases next to their spark plugs for ease of starting.  Not what you're looking for I'd bet.

Tobit

[Scott of the Sahara]

If displacement is equal shouldn't the turn over power needed be the same. Number of cylinders should not make a difference.
Now if the starter is geared lower, or the compression is higher that would make a difference.

[Triple Jim]

If displacement is equal shouldn't the turn over power needed be the same. Number of cylinders should not make a difference.
Now if the starter is geared lower, or the compression is higher that would make a difference.

Putting friction aside, a big cylinder requires more torque to get past the compression stroke than a small one.  So even if the power needed to complete two turns of the engine were the same, you'd still need more starter power with the twin, if a piston were just about to start a compression stroke when the start button is pushed.

[Mike Tashjian]

I think we are painting a false illusion about theoretical versus real world situations.  Anything from larger bearing surfaces to a certain type of valve train can add extra resistance and let's not even mention lubrication. Starter types vary.  It will always be better to have more energy available.  You may not want to haul a battery any bigger than necessary. At least understand that starting may not happen with minimum battery capacity. Especially if you encounter any adverse condition.    Mike 

[kevdog3019]

Check this out for cranking. https://m.youtube.com/watch?v=dKRW78g3Wo0

I think it will kick over my Guzzi 650.


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[kevdog3019]

Just purchased the SC-1 12oz. battery.  Capacity will be the question, but upon further investigation, I could run two in parallel essentially creating double the capacity and keeping with 12v.  These would be identical batteries.  We shall see, but I think I can make room for two if need be.  I will keep the revs up on this one for awhile to see what it gets me.  Now I need to wait for warm weather!  :'(

[Chuck in Indiana]

for good long spins in the twisties

In Michigan? Shirley, you jest.. ;D

[kevdog3019]

In Michigan? Shirley, you jest.. ;D

Yeah... I know, it's all relative.  I do live in one of the best areas where glaciers seemed to have cut out some good amount of relief.  Lots of up and down and all around backroads.  It might surprise you how fun it is.  At my doorstep fortunately.  No WV though.  I know twisties as I've been all over that state.  ;-T
 

[Chuck in Indiana]

Back in another lifetime, I spent a lot of time in Michigan.. riding dirt bikes. ;D

[kevdog3019]

Back in another lifetime, I spent a lot of time in Michigan.. riding dirt bikes. ;D

Yep... I'll admit I'm lucky to have the small plot I do for some good romps.  I've been on some admittedly "great" roads here in MI, and though they're scenic, they have a boring disposition for the ride itself in comparison.  This is mainly pretty deeply wooded area with some open areas.  Egypt Valley is what it's called.  There is a big PGA (I believe) golf tournament there every year.  Great course back in there.  I'm sure it's on the net and you might get an idea.