A few years ago we put up a short post about a fellow who made his own 694cc V8 engine with a homemade crankcase and his own crossplane crankshaft. Top ends come courtesy of engines from a Honda CB350F. The engine ran and sounded pretty sweet, but there was no information on it that I could find.
A quick run through the eBay listings this morning and something catches my eye, and sure enough, there’s the little V8. It’s mounted in a 1979 BMW R650 frame and runs through the BMW transmission. The engine has 8 Mikuni carbs and Petronics ignition with mechanical advance.
Dennis Franz is the man behind this little jewel, but it looks like the engine needs a bit of work and the bike would benefit from a little cleanup. According to Dennis, it shouldn’t be too hard to get things back shipshape and if someone bought this he’d have one beautiful conversation piece at bike night. Not bad for a little garage project. Check it out!
This auction is over.
Video below:
GenWaylaid says
Yeah, just take a week off from work to balance those carbs! It’s a pity the manifold he used in the video probably doesn’t fit in the BMW frame.
FREEMAN says
His post on ebay says it has a knock and he thinks it’s possibly a broken pistol. That’s a shame. Also… I would hate to have eight carbs. Beautiful bike otherwise.
FREEMAN says
Of course, by pistol I mean piston.
Mean Monkey says
Wow, I didn’t see this before on Kneeslider…….but I’d like to add it to the clutter in my garage!
My old lady would be ticked (I haven’t yet got around to fixing her Vulcan800).
Sasha says
If you can’t fix a Vulcan, buddy, you’re going to have a tough time with this thing!
B50 Jim says
Great effort, but I think you’d spend the rest of your life trying to get it to work right. Balancing two carbs can be a problem; eight would be a nightmare. I noted he has ridden it about 1500 miles — not a lot; he might have had a lot of sorting to do. Some years ago the midget car racers tried building V-8s using jugs from two motorcycle in-line 4s and discovered there’s a lot more to engineering a good-running V-8 than machining a crankcase and crankshaft. This would be a fun bike and I love the way it sounds, but there might be serious inherent issues that render it more of a curiosity than a good, rideable machine. Still, I applaud Dennis for having the gumption for building it. The overall effort looks well-done.. but those carbs… maybe it needs a fabricated manifold that would fit under the tank and tuck an SU (the world’s simplest carburetor) behind the vee. I’ve seen that done on an MGB that had a small-block Ford engine between the wells.
HigherRPM says
How about fuel injection? Looks like a GM L98 system might bolt up with a custom manifold, throttle body and some small injectors from RC Engineering.
Paulinator says
This is impressive. I think it would be easier to dial-in the eight carbs than to complicate the intake runners by feeding off of one or two carbs. I would have routed the intake runners in a cross-ram fashion, though, because the elbows look like centrifuges.
jack says
It’s amazing what a skilled person can do but a little more thought should have put into the cooling system. The owner stated that a piston is probably broken and I would bet money that it’s a rear piston because they are too hot. Should have been water cooled. I also agree with the cross manifold and why not use the Honda carbs that where on the heads. Still it’s a very interesting build and I am sure the builder was aware of these short comings and did the best he could with what he had to work with, I would love to see what he did next.
kim says
I’m running a Nimbus straight four with the engine mounted mort-south. The first cylinder gets the most cooling, #2 gets enough, #3 a bit less and #4 – lying in the slipstream – gets enough too. No reason to think it’s any different on the Honda V8, and besides it has a modern lubrication system and doesn’t have too work too hard for a living.
When Nimbus valves burn, or the big end goes, invariably it’s the #3 cylinder asuthorthat goes first.
Rob says
I remember reading that Chrysler Australia sent their entire 265 Hemi 6 cylinder racing engines to Weber in Italy to balance and tune the triple two barrel carb setup they were running in the 70’s it was too tricky for their mechanics…
anders says
I’m guessing then that the ’60s era Ferrari 365 GTC with 6 dual-throat Webers must’ve been a b*tch to tune … :^).
ACE
Paulinator says
I bolted a pair of Solex 26’s on my buggy…for a week-end. Ended up with a single down-draft Weber in the end.
B50 Jim says
Stick with SUs. They’re a snap to tune and synchronize; you can do a pretty good job using a screwdriver (or jet wrench on older models) and a short length of hose. Remove the air cleaners. Loosen the linkage between the carbs. Use the hose as a stethoscope at the carb mouths to set the throttles equally, then, using a small screwdriver, lift the slides 1/8″ one by one to set the mixture — if engine speed increases, lean the mixture; if it falls, richen the mixture; if it rises and then drops to idle, it’s good. Adjust the linkages so they open simultaneously, and tighten the linkage between the carbs. Top up the oil in the dampers, and you’re good for a few thousand miles. Leave it alone and drive. This procedure worked well for me on a ’73 MGB for years. I also fabricated a manifold to adapt twin SUs to a Plymouth slant-6, and it worked great — much better power than the old 1-barrel, smooth running and good economy. It even passed its emissions test.
Renegade_Azzy says
The quad carbs on my CB650 were easy to sync once I bought a proper set of carb sticks.
kim says
The bike has now been sold, for a mere USD 1,925.
MARK 5 says
Its pretty kool!