Hi, I'm doing a bit of engine research and have a couple of questions regarding the Gen I and II engines. (1) Does anyone know the Gen I cylinder bore pitch? (2) My understanding is that it is the same as the Gen II bore pitch but I may be wrong... i.e. the Gen II has a bigger bore but the pitch is the same for both. Is this correct?
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By pitch I assume you mean the stroke (the distance the piston travels from the bottom to the top of the bore)
Gen I Bore and stroke is 76 mm × 66 mm (3.0 in × 2.6 in)
Gen II Bore and stroke is 90 mm × 66 mm (3.5 in × 2.6 in)
The answer therefore is yes, the stroke (or pitch in your vernacular) is the same.
Gen I Bore and stroke is 76 mm × 66 mm (3.0 in × 2.6 in)
Gen II Bore and stroke is 90 mm × 66 mm (3.5 in × 2.6 in)
The answer therefore is yes, the stroke (or pitch in your vernacular) is the same.
Zeus36
Well-Known Member
The bore pitch is the centerline distance between two adjacent cylinder bores. Center to center between cylinders 1 & 3 or between cylinders 2 & 4 on the VMAX engine. It could be visualized as the center of one piston to the center of the adjacent piston.
It is also known as "bore spacing", "bore center distance" and "cylinder spacing".
Bore and stroke measurements can't tell you the bore pitch.
Either someone will have to measure the pitch or find it on some blueprints for both engines. I can't find any specs on the web or in the service manual that go into that much engine detail or show any engine blueprints.
It is also known as "bore spacing", "bore center distance" and "cylinder spacing".
Bore and stroke measurements can't tell you the bore pitch.
Either someone will have to measure the pitch or find it on some blueprints for both engines. I can't find any specs on the web or in the service manual that go into that much engine detail or show any engine blueprints.
one2dmax
Well-Known Member
I'm not sure what the angle is for either engine. Never bothered to measure it. Typically that kind of spec is listed in the owners or service manuals or even advertisements.
Not a term I have come across - thanks for the explanation.
Damon
Well-Known Member
Gen 1 70 degrees, gen 2 65 degrees
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Zeus36
Well-Known Member
All good info, but the cylinder "V" degree angle has nothing to do with the bore pitch. The bore pitch is a measurement between the two cylinder bores sitting NEXT to each other on ONE leg of the "V". This will be identical to bore distance of the two cylinders on the other leg of the "V".
Look down from the top of the engine from the rider's point of view and visually measure the center distance of the piston's circular vertices (center of the piston or bore circle) from side to side (left to right or right to left.)
Say these are the rear two cylinders looking down between your legs:
Look down from the top of the engine from the rider's point of view and visually measure the center distance of the piston's circular vertices (center of the piston or bore circle) from side to side (left to right or right to left.)
Say these are the rear two cylinders looking down between your legs:
Thanks Zeus36, yes it's the bore pitch that I am looking for. Unfortunately the pitch is something that is rarely listed anywhere so I'll just have to wait for someone that happens to be tearing down an engine. I'm also emailing vendors of second hand engine cases on Ebay trying get this measurement. I'm even prepared to offer some money for this service to cover the time taken to take a couple of measurements.
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Here's a shot of a project my machinist just took-on. It's a Honda 750 SOHC which has been bored-out to 1000 cc (!) but has 'problems.' I saw the cyl head gasket, a copper one, and the gasket had failed between cyls 1 & 2 and 3 & 4. Looks to me like too-little 'meat' separating them. The head's cracked, and he says he can save it. I have a '74 SOHC 750 awaiting restoration.
So I see this as a matter of 'bore pitch' and the ability of the head gasket to seal, and the cyl's to maintain their shape, and to conduct heat effectively. As far as I'm concerned, the guy should have bought a CB1100F to start. Before the H2O-cooled V4 Hondas were released, the CB1100F was the king of the Honda line. They flirted w/breaking into the 10's and were a good match for the stock Suzuki GS1100/1150's, the FJ1100's and the GPZ1100's. The guys who could ride those fast on a road course were the best riders. Freddie Spencer said the CB1100F's were "trying to go several ways at the same time," as the cornering forces overcame the frame's ability to not flex, despite the mods allowed in the AMA rules.
So I see this as a matter of 'bore pitch' and the ability of the head gasket to seal, and the cyl's to maintain their shape, and to conduct heat effectively. As far as I'm concerned, the guy should have bought a CB1100F to start. Before the H2O-cooled V4 Hondas were released, the CB1100F was the king of the Honda line. They flirted w/breaking into the 10's and were a good match for the stock Suzuki GS1100/1150's, the FJ1100's and the GPZ1100's. The guys who could ride those fast on a road course were the best riders. Freddie Spencer said the CB1100F's were "trying to go several ways at the same time," as the cornering forces overcame the frame's ability to not flex, despite the mods allowed in the AMA rules.
jedi-
Well-Known Member
Gen 1 is 146mm
one2dmax
Well-Known Member
I've got a gen 2 around here I can try and measure between centers
wildweasel_pt
Well-Known Member
Don't bother to find the centers just measure between walls on the same side which is going to be the same
Fantastic and thank you. Just out of curiosity, how did you come by this measurement? I've since bought a Gen II head gasket to measure it (when it arrives) and then compare the 2 (gen 1 and 2). I have to rush off to work now but I'll get back to you regarding this.
Once again thanks.
Phil
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jedi-
Well-Known Member
I measured a case I have, the web is 70mm and the bores 76mm. I did also notice the exhaust ports seem to be central so quick measurement says the same.If the gen 2 exhausts are central then someone only needs to measure the centres across the pipes to get you a size
That's the easiest way and works with a tape measure but for accurate results a vernier must be used and unfortunately due to their design, verniers can't accurately measure one side of one bore to the same side of another bore.
Thanks again for measuring this Jedi. Regarding the exhaust ports, it seems that unlike the straight ports of the Gen I, the Gen II's have exhaust ports that swing outwards.
Fantastic if you can and thanks.
wildweasel_pt
Well-Known Member
In that case measure between outside walls and subtract a diameter.
Thanks Fred, yes that'd work.
