I thought of a few more things regarding the big bores in a 305. The early Forged True 350 kits had a problem with the pistons seizing due to a lack of lubrication. The solution was to drill a very small hole at a dimension down from the top of each cylinder at the front, into the oil passage between the front studs. I know this works because my 350 kit came with the holes in the liners and I've done this to the liners I'm currently running. I can't remember the particulars offhand, but I have the info in my papers if you would be interested.
Before I installed the roller cam I used a Harmon Collins 7194 cam with lightened rockers and S&W valve springs. The very low pressure of the stock oil pump did not provide adequate lubrication to the valve train and cams and rockers would gall and wear, requiring frequent replacement. I solved the problem by building a dual oil pump, with two sets of gears. It was actually pretty easy to build and in addition to a second pump body and gears, I had to make a longer shaft. I still have one I'm probably going to use in a stock motor I have. I could provide some photos and more detailed information if you are interested. The roller cam eliminates any need for additional lubrication though.
I have also installed an oil cooler on my engine that has really worked out well. With the big bore my engine always ran really hot before I added it. I'd be glad to share how I did that as well.
What are you using for a head gasket? I used to be able to find oversize head gaskets but have not been able to find them anymore. I was originally going to make solid copper head gaskets and o-ring the cylinder but before I got around to competing them I came up with a simpler solution that has so far worked fine. I took a new CB350 head gasket and cut out a pair of donuts, from the fire ring out, a quarter of an inch. I then cut out a new CB77 head gasket to fit the pieces over the cylinders and installed the head. I've had no oil leaks and more importantly no combustion leaks.
Last, what spark plugs are you using? I found a hand full of NGK D-12H racing plugs several years ago and am using them. They are of the old side-electrode type. Years ago when I was still running the stock ignition, you could not start a cold engine with them, they were so cold, they'd foul. I had to put in a set of street plugs, warm the motor up and then swap them just before heading out on the track. The Dyna ignition and coils are hot enough to fire them right up in my engine now. They let me lean the engine out and it really wails with them.
CB77 RacerThe engine had a gasket in it already, looks just like a stocker! I have a 3mm oversize head gasket for the bike I'm doing now. There is / was a seller on Ebay selling 64mm piston kits for CB77s, user name eludes me right now. He aslo sells head gaskets in that size. I've also seen an Ebay seller that will make any head gasket out of copper.
It has D8HAs in it now, but we haven't really run it much. In the box of goodies were a set of D8HAs with the electodes removed :-) I am intersted in all of your mods for sure! The CB77 racer had one passage for an oil coller drilled and tapped on lower left of cylinder, I'm not sure where the second line would go. I'll PM you with direct contact info, as I'd love to speak with you in person! Davo
CYB 77Hello Davomoto
Thats a nice machine / project you are working on. Are the pistons Forgetrue or Hepolite cant realy tell from the tops ? I had a 64mm cylinder with little slots in the liners it was before this site was on the go and a while before someone explained what they were there for. ( CB77 GUY, at first I thought they were "damaged" before I had a better look) The bike has some nice CYB bits as well, look forward to seeing more photos as it progresses. Gordon SAFOJ Gordon,
Not sure what the pistons are, except that there was Powroll Literature in the box of CYB goodies, with tolerances and such, so I'm asssuming that is where they came from. Progress is at a standstill right now, waiting on owner to make some decisions concerning rear fender, frame bracing, colors etc. It's really quite close as it does run well! Davo
Davo,
Thanks for sharing your Honda, you have a good project there. 64mm head gaskets are available from Bill Moeller at Bore Tech: http://bore-tech.com/categories/honda-305 He has custom gaskets made by Cometec. The composite gaskets are very good, I have used them in CB350s and CB450s. I have never seen extra oiling holes or grooves in four stroke cylinders before, very curious! In my experience, a seized piston is from too much heat for the engine to expel, too little piston clearance or a poor piston design. Stan
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