Topic: STROKER project, keep your children away

[mec]

too much time and strange ideas are born.
what to do, when the racing engine explodes? you need a spare engine. not underpowered, its always good to have some horsepower.

the idea: i want to do a stroker engine, 1000ccm pistons, dohc 900 crankshaft with +6mm more stroke. this will give ~1100ccm.

but there are some problems to be sorted aut:
the 900 dohc crank has a "reverse" layout, ignition on the left side, alternator on the right. primary drive is a hivo chain, camchain ditto. 6mm more stroke will need shorter conrods or a 3mm thick base gasket. will the higher cylinder height be compatible with the length of the camchain? what about the chain tensioners? at the moment i do not know, what problems will occur furthermore, nor do i know, if i will have success finishing this project.
all i know is, that there are stroker engines with cb900 crankshafts outside running pretty well.

as for my 1000ccm engine i will use a F2 crankcase with the double bearing at the end of the transmission. cylhead will be from an early K modell. a webcam 315 will do the valve job.

my work started with investigations on the primary drive. it seems that the primary sprocket of an early gold wing will fit.
primary chain can be done by two prim chains of a cb 900 bol d´or.
tensioner: i hope i can take the rubber guide from the cb900, without the oil pressure activation, spring preloaded only.

what i have done so far:
i put the 900 crank into the sohc case to see that the crank does not spin free. there had been minor edges in the upper case that i grinded away. i believe a lightened crankshaft would have enough room to move, however.
next step was to machine the crankshaft to my plans. all i wanted, was to have the ignition on the right side (cranshaft seal from a bol d´or fits to the sohc case). i removed the crankshaft cone on the lathe and prepared the right end exactly as it is on a sohc crank. now a stock ignition from our 750 fits to the 900 crankshaft. drilling the hole for the stud was a bit tricky because of the existing obliquely oil feeding holes, but it worked. on the left side it will be possible to adapt an alternator, driven via belt or possibly directly mounted to the crankshaft.

[mec]

i was unhappy because i could not find a camshaft sprocket for the hivo chain fitting to the crank and cam.
the one from the bol d´or is a crippled one. does not fit to our cam at all.
i tried to make it fit to our cams.
lathe, welding, mill and voila.......perfect fit to the cam. BUT..........0.3mm oval and spins like a front wheel after a severe frontal crash.
the welding has not done good to the sprocket. this sprocket is good for the garbage container. clueless what to do for the moment.

next step was doing some measurements on camchain length. 3mm (half the way of the +6mm stroke) thick base gasket will do no good to the camchain tension. using the bol d´or camchain means that it will have to be shortened anyway. but the complete height from crankshaft to camshaft is now unfavorably. eventually it will be necessary to replace the oem basegasket by a 4mm one, so that the comression ratio will be in a reasonable range (i do not want to have more than 10.5:1). this would do good the camchain issue.

thats it for now.

mec

[Terry in Australia]

Ooooher, more mechanical porn from our Austrian master racer!

[manjisann]

I didn't understand much of it, but I like the pics!! Someday I hope to understand how to operate those nifty machines!!

Brandon

[Frankencake]

"Quote"  Too much time and strange ideas are born.  "Quote"

Yeah.  Useless things like the telephone and internet, internal combustion engines, drag races, beer, ping pong.
  Quite frankly, I'm glad that people get bored so easily.  What you are doing is better than wasting your life in front of the television like most people and you'll have something to show for it rather than a beer gut.  (Not that a beer gut is bad to some of you out there.)

[Retro Rocket]

Hello Mec, there is a guy in Australia that is building engines with the Boldor crank and races them very successfully. His name is Rex Wolfenden, Terry knows a great deal about this guy and may be able to get some answers to your questions or even put you in touch.

Cheers Mick

[mystic_1]

It's a shame about that cam sprocket, it looks nice in the pics anyway

I think it counts as an "offering to the god of speed"

mystic_1

[Terry in Australia]

I can ask Rex what he uses if you like Mec, I had a look at Axels site (Satanic Mechanic) and he says he's considering using a CB250/450N cam sprocket, but I imagine there's still some requirement for some machining to make it fit. Cheers, Terry.

http://www.satanicmechanic.org/bigbore.shtml

[mec]

Hello Mec, there is a guy in Australia that is building engines with the Boldor crank and races them very successfully. His name is Rex Wolfenden, Terry knows a great deal about this guy and may be able to get some answers to your questions or even put you in touch.

Cheers Mick

I can ask Rex what he uses if you like Mec, I had a look at Axels site (Satanic Mechanic) and he says he's considering using a CB250/450N cam sprocket, but I imagine there's still some requirement for some machining to make it fit. Cheers, Terry.

http://www.satanicmechanic.org/bigbore.shtml

thanx, any help is very appreciated.

some days ago searching the cam sprocket, i found a detailed view of the camchain for the cb250/450N. it seemed to me narrower than the 900 one (what makes sense cause of the fact that it needs to actuate less and smaller valves).

mec

[Jerry Rxman Griffin aka MuthaF'er]

Mec,

That 900 crank looks quite a bit larger. How much weight differential is there? Are you planning on lightening it?

Jerry

[mec]

yes, the cb900 crank is larger, however the same bearings.
weight:
sohc 9.8kg
dohc 900 11,6kg

all the investigations on lightening the crank said, that it should be possible to do it by myself. for balancing however, i have to bring it out of my house .


in the meantime i did some further measurements. the cranksprocket including the hivo chain is D=52,5mm, the camsprocket with chain D=99mm.
sohc for comparison: at the crank 49mm, camsprocket 90mm.
this means that i will have to reposition the camchainguide approx 3mm to the exhaust side.

mec

[lordmoonpie]

Mec, have you had a look at my engine build thread on here? I had a lot of the same problems you are having now as I put a DOHC 750 crank in a SOHC motor.

http://forums.sohc4.net/index.php?topic=32541.0

The primary drive I used was from a GL1000, rivetted back onto the 750 shaft. You'll need to get heavy duty primary rubbers though or it'll tear apart with that extra power. I also modded the oil pump and cases to fit the DOHC tensioner on the hy-vo primary chain and pressure it with an oil feed off the pump.

Cam sprocket was a custom made item but very simple. It's a combination of a CB700 sprocket for the hyvo teeth with a SOHC set of holes machined out of the middle. Problem I found was that if you keep the thing as thick as a CB700 hy-vo sprocket, when it's all bolted up the sprocket bolts foul the camchain tunnel and would smash to bits running. Solution is to dish out the middle of the sprocket to SOHC thickness out to 5 mm beyond the bolt holes and then it all fits in fine. I think there are pictures of mine on the motor thread. I talked to Axl about his recommended sprockets but the CB700 was the closest I could get to and keep the necessary 46 teeth to maintain crank to cam rotating ratios.

Hy-vo camchain really doesn't fit nicely in mine as there's a 1.5mm longer rod to cope with the DOHC crank differences - you will have the problem the other way with shorter rods. I got a custom camchain slipper tensioner made by KAS Performance in the USA - about $200 but well worth the money. This with a bolt in the back of the tensioner adjuster to give a little extra pressure works fine. The front tensioner blade needs replacing too as it needs the track for a hy-vo. I used a CB200N blade cut down at the base. They're obsolete now so you have to hunt for old stock.

Finally, the hyvo camchain doesn't clear the inside of the cam cover so I cut a fair chunk out of the insides of the cover, thinning it right down to about 2mm in places, then it all goes together.

Does it run well? Ah - still working on that one, hopefully this weekend but then Miek Rieck will tell you I say that every weekend

PM me if you want any other details - happy to pass on the benefit of six years of my mistakes to save you making the same ones!

[Ecosse]

if you big brains (i say that with all humility) don't mind an underling question; why not have a billet crank ground to your specs? is it a $$ issue? or in mec's case, €€.

[mec]

Mec, have you had a look at my engine build thread on here? I had a lot of the same problems you are having now as I put a DOHC 750 crank in a SOHC motor.

http://forums.sohc4.net/index.php?topic=32541.0

The primary drive I used was from a GL1000, rivetted back onto the 750 shaft. You'll need to get heavy duty primary rubbers though or it'll tear apart with that extra power. I also modded the oil pump and cases to fit the DOHC tensioner on the hy-vo primary chain and pressure it with an oil feed off the pump.

Cam sprocket was a custom made item but very simple. It's a combination of a CB700 sprocket for the hyvo teeth with a SOHC set of holes machined out of the middle. Problem I found was that if you keep the thing as thick as a CB700 hy-vo sprocket, when it's all bolted up the sprocket bolts foul the camchain tunnel and would smash to bits running. Solution is to dish out the middle of the sprocket to SOHC thickness out to 5 mm beyond the bolt holes and then it all fits in fine. I think there are pictures of mine on the motor thread. I talked to Axl about his recommended sprockets but the CB700 was the closest I could get to and keep the necessary 46 teeth to maintain crank to cam rotating ratios.

Hy-vo camchain really doesn't fit nicely in mine as there's a 1.5mm longer rod to cope with the DOHC crank differences - you will have the problem the other way with shorter rods. I got a custom camchain slipper tensioner made by KAS Performance in the USA - about $200 but well worth the money. This with a bolt in the back of the tensioner adjuster to give a little extra pressure works fine. The front tensioner blade needs replacing too as it needs the track for a hy-vo. I used a CB200N blade cut down at the base. They're obsolete now so you have to hunt for old stock.

Finally, the hyvo camchain doesn't clear the inside of the cam cover so I cut a fair chunk out of the insides of the cover, thinning it right down to about 2mm in places, then it all goes together.

Does it run well? Ah - still working on that one, hopefully this weekend but then Miek Rieck will tell you I say that every weekend

PM me if you want any other details - happy to pass on the benefit of six years of my mistakes to save you making the same ones!

thank you for the link. beautiful work, you have done.
a lot to learn for me and a lot of my questions answered.



@ecosse:
a billet crank is very expensive. and most of the issues are unsolved still (tensioners and guides, camsprocket, prim drive).

mec

[Tretnine]

This project is way out of my pay grade, but I'm interested none the less. I want to see how this turns out.

[Ecosse]

This project is way out of my pay grade, but I'm interested none the less. I want to see how this turns out.

did you see his egli replica?
http://forums.sohc4.net/index.php?topic=44736.0

[lordmoonpie]

thank you for the link. beautiful work, you have done.
a lot to learn for me and a lot of my questions answered.

mec

Mec - I'm flattered you think my work is good. One day I will have the skills to build something like your Egli replica but that day is a long way off. Best of luck my friend 

[mec]

two days ago i ordered some essential parts as camsprocket, gl1000 primary drive sprocket, camchain guide and tensioner.
curious, if all will go to australia again

in the meantime i saved 600gr from the 900 crankshaft, now weighting 11kg.

i cnc´d a 3mm wooden basegasket as a temporarily spacer to see the camchain tension with the 6mm longer stroke. 3mm are not good at all, the bol d´or camchain has to be shortened by 3 links and will be very loose yet.
i am thinking of a 4mm spacer and the use of bol d´or rods (1mm longer than sohc rods). will do some more measurements. maybe this will lead to a reasonable camchain tension. all this calculation are done with the use of stock height pistons.

a 3-4mm spacer will require some headwork to be done to accept the HDstuds washer and nuts, however.

i try to avoid the use of shorter rods. shorter rods will do no good to performance, i think.

mec

[turboguzzi]

Hei Mec

Nice work, always envious of your workshop! (and your craftmanship too)

About your crank, although its done now, you might want to check the pics that HB1-fan sent me in this thread

http://forums.sohc4.net/index.php?topic=55272.msg596892#msg596892


In the thread about my own bike development I posted some pics of the chain tnesioner I am usiong now, might be useful for you

http://forums.sohc4.net/index.php?topic=55162.msg593605#msg593605

TG
 

[mec]

thanks for the link. i am following your threads with great interest.

many years ago i had a lightened and balanced crankshaft machined by hoeckle (here well known for their excellent racing cranks). this crankshaft was cut the side of the webs.
some days ago i (picture)googled "hoeckle crankshaft". surprisingly i found a crank knife edged. cause time does not stand still, it seemed that hoeckle has learned something. thats my interpretation.

in the meantime i checked stacking height, piston height, conrod length and camchain length one more time. it turned out, that with the stock cyl and cylhead height, with the stock gaskets installed, the hi-vo chain has a good length to fit a adapted chain tensioner.

that means that i will use custom 1000ccm pistons, maybe the piston pin moved upward as far as possible. conrods will be custom carillos, shortend by 3mm minus the length the piston pin will be moved up.

i am not extraordinary happy with shorter rods, maybe this will cost one or the other HP, on the other hand adding more height would cause some inconveniences: the HD cylstuds are too short, custom gaskets are necessary, more overall height will not fit my frame.

mec

[mec]

here we go again:
some more spare parts arrived. the pictures show the dissasembling of the primary drive, drilling the rivets.
the primary drive with the hi-vo chain is from a GL 1000, all the internals are the same as our sohc ones.
pic # 3 putting all things together
pic # 4 show the old rivets and some new one made from mild steel.
pic # 5 the primary drive on the main shaft

[mec]

the hi-vo cam chain sproket is from a CB700 (thx for the tips from this forum). it has the demanded 46 teeth and the correct width. unfortunately the inner diameter is way too big and needed some hours on the mill.
it took more than one day to machine a hub suitable to the camshaft and the new sproket and sitting inline with the crankshaft sproket too.

first pic shows some steel on the mill making the outer contour
second pic shows the stock sohc sproket on the left, the cb700 in the middle and my unsuccessful one on the right.
on the last pic you can see that there had to be some material to be removed for the cam chain guide (from a cb900 dohc).

[mec]

this guide works pretty well, however the slot in the cylinder had to be reworked and the guide had a sort of "bumper" on the rear side which had to be downsized.
again there was some material to be removed in the upper crankcase (pic 2).
time to start the work on the camchain tensioner (pic3).
the tensioner body was made out of 1.5mm steel, the tensioner guide was a cb900dohc one. i wish to find a cheaper solution for this tensioner, because i had to buy a complete cb900 tensioner. i have seen that there are tensioner available which can be disassembled and one can buy the tensioner guide alone. but i was not sure if they have the correct width.
instead of the sohc tensioner body, i made a 8mm aluminium plate. the self made tensioner is screwed to this plate with a 6mm screw and a 8mm screw which is also an adjusting screw. the adjustment of the chain tension is made by hand solely.

[mec]

as can seen in the first pic, the alu plate is not a beauty. i think it will go again on the mill for some "beauty work".
last picture shows camchain tensioner and guide installed, hi-vo primary drive and a way too short cb900dohc chain.

mec

[turboguzzi]

nice work mec...

....but also have to ask: why did you have to go for this solution where the hinge of the tensioner puts a bending load on the adjuster plate through the "L" beam that you built? Why couldnt you attach the hinge somewhere directly to the head and just press the blade in the middle?

BTW, we have a UEM vintage Endurance race in Franciacorta, in the north at the end of october, you might want to come to that one....

TG