2 bikes into 1, insanity has started

hello everyone,

I just picked up a 83 750f, the petcock unknowingly leaked gas into the engine so I have taken all the covers off and am cleaning everything out. When I got to the stator and unbolted it this little piece of aluminum fell out from behind it. It doesn't belong to the stator, transmission, or valve train. its perfectly clean and is stepped with a slight curve.

I am currently in the dark as to where this piece came from.

Thank you for any help!

 

https://ibb.co/doFQWv

 

It looks like a piece that has broken off some casting. You will have to inspect all parts to find out where it came from and why it broke off. I would use one of the small bright LED flashlight to see better. Could also be left behind by a previous stator change, since it can't get into the main engine, shouldn't be a problem.

 

thank you for the quick reply. This bike has only 13K on it, so far everything is OEM, CLEAN, and almost no wear on ANY parts...deal of a lifetime! I will inspect further, drop the pan as well to see if anything is in the oil pump strainer. hoping its not a problem as well.

 

Wow great find
Pictures and welcome to the madhouse


Sent from my iPhone using Tapatalk

 

I knew that piece was part of a piston...

https://ibb.co/fP3t3a

bent rod and broken piston, torn into the bike lastnight, hoping to get the cam chains off and drop the bottom of the block out by the weekend. this was the progress for tonight. Also found sand in the slave cylinder

https://ibb.co/mH8Xwv
https://ibb.co/m9aebv

This is my first motorcycle but I've been working on 80s Hondas for 15 years, its comforting to know a lot about Hondas!
Time to see how the cylinder wall is from the bottom and plan accordingly.

 

Your picture hosting site isn't working for me. Maybe others too are affected.
You can upload pictures I think.

 

Ouch, worse than I thought. Good luck.

 

got the engine out of the bike tonight, tomorrow I will be taking the bottom half of the block off and figuring out how to get the cam chains off.

hoping the cylinder wall(s) are okay, if not then maybe an overbore. new crank will be on the list of course.

can anyone tell me what were the design flaws in the crank? oiling issue? I'm thinking of taking the crank, bearings, and rods to a machinist to open up any oil passages in said parts.

attached are the pics: first piece I found, bent connecting rod where you can see the crank counter weight going into the piston, and the engine out of the bike

 

OK, that looks terminal. Before you start spending money on this please be aware getting parts for these bikes is very difficult and expensive.
The 750 has its fans but it's probably the most prone to serious engine problems as it was the first of the breed.
I would think really hard about trying to resurrect the engine. You would be better off trying to find a second hand engine although that is also not easy these days. Its a very old bike and didn't sell that well in the first place so it has to be a labour of love.

 

thank you for that reality check. I've already sourced the whole rotating assembly, nothing about oversized pistons though so if the walls are scorn then a new bottom end is in order(I'm stubborn)
The bike itself was $700 and only thing into it is my time so far. I do enjoy the look of these bikes, even the 2nd gen doesn't appeal to me.

I have looked into engine swaps, the 1000cc I am capable of doing but I would rather do a direct swap of a newer, "resolved" 750cc or higher, haven't found information on that.

Anyone know of the specifics of any crank issues?
Any direct swap of a, "resolved" 750cc+

 

I don't see how a 1000 would work, it is a much bigger, heavier, longer engine. I have had my 750 since 83 and dearly love it, but if the engine goes, that's it.

 

A much better bet would be a early VFR700/750 engine. Must have been tried before.

 

1000 motor in a VF750F frame has been done. The architecture is basically the same.
Look for "The Gimp". 1000 into 750 swap. Think it was an R motor.

 

Got the crank out, didn't know the pistons will only come out from the top!

Crank looks perfect, no heat marks or odd wearing in the bearings.

I'm going to take a guess and say the previous owner hydro-locked the engine with gasoline? Is that possible?
He said one day it just wouldn't start and didn't wish to put money into it thinking it was electrical.

 

got the heads off and pistons out...#1 was bent, cylinder #3 is scored. cylinders 1,2, and 4 look great. I'll be taking the upper block to a local machine shop tomorrow to see the options.

 

a force that bent the rod that much could possibly have bent the crank too.

 

Yep!

local machine shop said if I hone it I will still have some blow by. Able to find a guy in upstate New York who could re sleeve it, that would run about $350.

right now I will hold off on doing that and just source a running motor. inspect and replace any parts and swap it into this bike. In time I will have the crank checked and the sleeve redone but I would really like to ride this bike the more I look at it!

the quick plan after some riding is to weld and fabricate some HRC inspired parts. the air intakes on the front fairing, the 4-2-1 passenger side exit exhaust, better rear shock, thicker weight front shocks, oil mod with 1000 pump and pan, smaller front sprocket and eventually lighter weight wheels. I have a problem with all things mechanical! everything goes out the window once its in my hands, hell ill get a cam re-grind or aftermarket ones later on. bore out the carbs and MAYBE shave the head if possible on the rebuild of the original engine...

driving to Canada soon to grab a new motor and anything else I can

 

That would be my guess. Having bent a rod in my 2000 Ford F150 I know how quick and easy this can happen especially if the water jacket seal leaks into the intake.