I’m new to the forum but I have been a VF owner right out of high school, buying my brand new “84” VF700F. A few years later, I was lucky enough to acquire the VF1000F. Both are kept in very good condition without any engine issues (cams) except the occasional carb rebuilds and both bikes have over 25k miles on them. However, recently I was trying to diagnose a slow starting problem on the VF1000F. It turns out that a vendor misdiagnosed a faulty starter and said the starter was fine. I then went internal and long story short, I broke the interim starter gear case sleeve (mybad)!!! This holds the gear shaft in place and I patched it with JB Weld but it didn’t last long (2 yrs). It turned out it was a bad starter.
Here is my question, I think I found a donor engine and would like to swap the lower cases from my perfectly running engine with the bottom half of the donor motor. Can I do this with minimal surgery to the engine?
You can probably swap them but you must remember, the main and rod bearings are size matched or “colour coded” to the crank at the factory, yellow, green and brown, depending on journal sizes etc… essentially the bearings need to stay with the crank. Not too sure whether the case halves are matched to each other though..? One would hope not.
Its funny you mentioned the two halves being machined to match because the local mechanic just mentioned that to me as well. Yours and his comment made me ask the guy holding the donor motor the question of “does the motor run?”
Fingers cross this all works out and I can continue to keep both going.
They are. Bearing colour selection is a function of determining crank journal OD and crank case ID. The crankcase bearing bore sizes are coded and stamped on the rear of the cases when the machinist measures the finish size. They can’t do that if they’re working on separate unmatched case halves.
Yep that’s correct. All Honda cases (and I would think most manufacturers) are matched at the factory. Don’t understand why wreckers sell and people buy them separately, cause you are just looking for trouble if you do. Depends how many miles (km) this donor engine has done, you may be able to make one good engine using the best parts from both. Whatever you decide, it is going to be a big job and you will have to know what you are doing, or it will also be an expensive one too. Luckily you have this forum to help with advice if you decide to do it yourself.
John
I would suggest getting it welded and re-drilled - using a really reputable welder. This may be a better option. Could it be done without removing the engine? The key is getting the hole re-drilled exactly perpendicular. An expert welder might know exactly what to do and could advise.
Another option would be to visit an engineering shop and see if they can machine away the damage with a cordless drill mounted hollow end mill or annular cutter. A threaded shaft screwed into the threaded hole that fits inside the cutter would pilot the cutter and maintain squareness.
The casting that is machined away can be replaced with an aluminium or steel spacer sized to suit. I did this with a broken oil pump boss but of course the cases were fully disassembled and the operation performed on a milling machine.
There you go. you have three suggestions already and I think you will get more.
Another one would be to check the numbers and letters on the donor motor. You never know they could be the same as yours? Weight them all up carefully before making your mind up. Getting a good machine shop to weld and redrill or drill and use a spacer while still in the frame would certainly be the cheapest and quickest way to go.
John
Good morning all. Thanks for the suggestions- keep them coming!
Gosh, lots to think about… I’m good at maintaining these engines, but a repair like this, involving motor tear downs and rebuilding, I don’t trust myself. So it will probably end up costing me mucho $$.
The way I’m starting to think is, the 1000 doesn’t owe me anything, it is a great bike (I do prefer the 1000 over the 700) but it is what it is.
