classic motorcycle forum
Motorcycle Discussions => American Bikes => Topic started by: s2airflow on December 04, 2011, 10:45:53 PM
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If a Chief is stroked from 74" to 80" is there anything else involved other than changing the flywheels?Thanks.
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Don't the heads also need to be the 80" type ?
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Either the barrel height was increased to allow for longer stroke or they raised the gudgeon pin height.
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74in 1200cc boar 82.55mm stroke 112.7mm side valve is this what you have ? and want to go 1340 ?
raised the gudgeon pin height? does not effect stroke , one way is a offset crank pin a common cheat about 7mm for 140cc in this case but they can come lose , make sure you have clearance at bdc for skirt , big boaring some motors can make them slower ie moto guzzi le manns , for more power side valve heads can be worked with good effect
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Read what i said again!
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i have , what is your gudgen comment refering to ( compresion height does not effect stroke ) ? indian never made a 1340 as far as i know so what is your point ?
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you definitely cannot stroke a sidevalve engine by simply putting in different flywheels as the piston crowns will hit the combustion chamber roof.
You either have to use longer barrels, shorter connneting rods or pistons with reduced compression height or a combination of all three to counteract the increased stroke.
I think that is what rogerwilko meant.
Cheers
Andy
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i would just pack the barrels , as i know this works as ive done it , no need to change pistons , on ohv engines ( and sv ) this does alter the valve timming in relation to piston position but is to small to be of concern , i am not a fan of this route for power (bhp ) as it does not work , but the sound is lovely
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Indian went 80" for 1950.
80" heads have a recess to allow for the pistons.
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Raising the gudgeon pin height on a piston effectively lowers the piston on the rod. Lots of manufacturers do this when stroking engines.
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you can put the pin where you like altering compresion height , but it will not alter the stroke at all , if this is common practice does any one know why they do this ? i might see the benefit with big boar kits ( piston weight etc ) but for a longer stroke i can not , did indian move the pin when they went 80 ?
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You're a pain in the arse! Who said anything about gudgeon pin height altering the stroke! Read it again!
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Either the barrel height was increased to allow for longer stroke or they raised the gudgeon pin height........i think that was you ? have you alsymers? i understand
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Well that reads to me that they either have to lengthen the barrel or raise the pin height to ACCOMODATE a longer stroke, but hey Im just a by-stander
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Hey
Come on Wetdog, read all the posts and replies again, then you should understand what Rogerwilco is saying.
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i have read a few times now and he appears to say that wrist pin height is some how connected to stroke , and when stroking a motor this needs to be altered , and in fact , is common practise , sorry but thats rubbish , i would agree with big boar motors , but i think he maybe out of his depth here , but i am still waiting for the evidence and will admit to being wronge if i am , i dont think im talking out of my arse as i have some experience in this area turning side valve ariels vbs into ohv motors
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OK,
The original post asked if "anything else needed to be done other than changing the flywheels", obviously if you do this to increase the length of the stroke it is likely that the piston can hit the head, this can be avoided by using a piston with less height above the gudgeon pin, fitting a longer barrel or packing the bottom of the cylinder block, to name the most common ways.
HTH.
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The world is still flat Wetdog! Don't go over the edge! Think of the difference between an M20 BSA and an M21, the M21 was stroked to get 600cc and they used the same barrel but the piston was the same boresize. What did they do for expediency? They raised the gudgeon pin height on the piston.
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o dear m20 82 by 94 mm m21 85 by 105 mm as thought your out of your depth , keep taking the medication . is the world flat or just the top of your head .
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Pre-war 85mm, others 82mm. Give up!
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sorry showing my age there but you forgot to include the date , but what you are saying ( i think ) is they moved the pin to acheve this stroke , i dont think you are giving them enough credit , they like all else out there know moving the pin has no relation to stroke . draw a little diagram and lets say swept volume 50cc now move your pin down ( on the piston ) 3mm and pack the barrel up 3mm , what is the swept volume now , please let me know the answer
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As my Mother used to say, "there are non so blind as those who will not see".
So I will now leave you to fall out over something which you really agree on, but one can't see it.
All the best to both of you.
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Not heard that one , but as my old dad used to say
“ lifes like a shit sandwich , the more bread you have , the less shit you have to eat “
really has nothing to do with this post , my point is by moving the wrist pin you are not altering the stroke , its really that simple
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my point is by moving the wrist pin you are not altering the stroke , its really that simple
And nobody in this entire thread has ever suggested anything like that!
So wlll you please let it rest now.
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I'm tired now. Think i'll have a nap!
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Either the barrel height was increased to allow for longer stroke or they raised the gudgeon pin height
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Ok, wetdog, one last try:
Either the barrel height was increased to allow for longer stroke or they raised the gudgeon pin height
This was rogerwilkos ANSWER to OP's question: "is there anything else involved other than changing the flywheels" when stroking a motor.
So it was a known fact from the beginning that a longer stroke is achieved by putting in flywheels which have an increased crank throw. But to accomodate them and to avoid stamping holes in the heads with the piston crowns, you have to do something else: INCREASE THE BARREL HEIGHT or else RAISE THE GUDGEON PIN HEIGHT by putting in pistons with less compresson height.
That is exactly what rogerwilko suggested and nothing else.
And f you still don't get it now you'll never.
And this is the last from me in this matter.
Cheers
Andy
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good fun tho
i reckon on that boar stroke was incressed by @6/16 so i would stay with existing pistons and just pack the barrel 3/16 or try looking for pistons which may not exist , which way would you go ? this is the best advice i can think of to someone trying this
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Since Indian 80" heads provide a recess for the pistons in the 80" (stroked) models, consider how much of the 'discussion' here is relevant. ?
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i agree , but im boared , been waiting for a manxman tank to be finished for over 7 mounths now and im going mad
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I prefer to be stroked rather than bored.
Sorry couldn't resist that one.
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very good , my son used to have a t shirt that said "id rather be blowen than injected " mine said" keep on truckin" , now i am going mad and taking some with me i fear
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