Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: larry on September 14, 2006, 11:59:21 PM

Title: Engine froze up
Post by: larry on September 14, 2006, 11:59:21 PM

1974 750...been idle since 1989... 35K miles...stored in a dry basement..small amt of water on floor maybe once every  5-6 yrs....dries up in no time........i am original owner...please give me some ideas what I can put into cylinders to attempt to free them up... WD 40.....penetrating oil....10w-40...Rust buster.....is there a specific product for this purpose?...gas was drained in 1989......will motor have to be torn down??

  i used to kick this thing over once in awhile just to prevent this problem...been awhuile since i did it i guess......assuming I do get to free up...........what then besides the obvious like  drain oil, carbs, fork seals, brake probs,etc

  I can let this sit all winter with some kind of lube in cylinders if need be

  Thanks guys.

Title: Re:Engine froze up
Post by: Spitfire on September 19, 2006, 01:59:28 PM

Hi Larry,
             Sounds like you have a real problem there, my 76 CB750F sat in my garage for 12 years without being touched and it spins freely. But when I stripped it I found a nipped up top compression ring on No. 2 cyclinder.
I did buy a 77 CB750F2 that had sat outside in the English weather for 2 years and was locked solid, took the motor out and spent a long time with WD40 and large rubber mallet/pieces of wood to strip it down. Had to do a complete top end overhaul, new rings pistons etc.
If it were mine and I was in no hurry I would pull the plugs and squirt WD40 into the cylinders and periodically try to turn the engine. But not that I am no expert, presumably if the engine used to spin up and it has not been run up there should be no problem with the bottom end or gearbox.
However even if you free it off, you will not know the condition of the pistons/rings and cylinders. If it does free off do a compression test to try to gauge how healthy it is.
There may be better additives out there but I do not know of any.

Good luck

Title: Re:Engine froze up
Post by: JonnyB on September 20, 2006, 11:07:42 AM

Hi Larry,

When I got my F1 it had a full overhall and then it had been stood for about 4 years. I got it started hopped on and drive away, 10 mile later and a siezed camshaft I realised I should have stripped it down and rebuilt it.

As Spitfire says, put a penatraiting oil down the bores. But personally I'd drop it and visually inspect the bores, pistons and valves. oil it all up and put it back together.

If you have the time, don't take the risk, parts are hard enough to find as it is