New Start After Sitting 34 Years

[ScottG]

Hello,

I'm new to the forum. I just acquired a 1971 CB750 which has been sitting 34 years and is a bit rough. I have worked mostly on BMWs, but I'm very excited to be working on a truly classic Honda. I'm planning to do a full restoration.

Thankfully after letting Marvel Mystery Oil soak in the cylinders for a few days, the crank turned with no effort at all. When it was stored the plugs were in place, so that was a good thing. After draining the tank, sump and replacing the filter, I had a few questions.
1. Given that it is critical to have the pump primed, would it be beneficial to add the new oil as follows: 1 quart to the sump and 2 quarts to the tank? If so how and where would I add the oil to the sump?
2. The oil was very black (as expected), but the filter was quite clean, thankfully. I'm inclined to drop the sump pan and clean out the inevitable sludge, as well as clean the oil pump screen. I'm assuming this is highly advisable given how long it has sat?
3. I would also like to remove the leftover oil from the tank after I drained it. Is it best to suck it out or remove the tank? If removing is the best option, should I remove the oil feed and return hoses from the tank itself, or from where it connects to the engine? I will be replacing the o-rings either way.
4. Given that the oil filter is horizontal, is it beneficial to add some oil to the filter before reinstalling it - just enough so it doesn't spill out excessively when installing it?
5. Lastly my gas tank cap does not want to open - it needs to be replaced anyway, so what is the best method to remove the cap?

Once the new oil is in, I plan to rotate the crank bolt (right side) back and forth until it can rotate smoothly 2-3 full turns. I have lubricated under the tappet covers as well. It will be awhile until I try the first start, since the electrical and carbs need to be sorted first.

Any advise is much appreciated!

Scott

 

[hinksy]

Hey scott , welcome to the money pit . Do you have a bore scope ? I would check out how the valves look first . My F2 from missouri sat for 30 and it would never have ran properly as most of the valves were toasted from sitting open , and that is with exhaust on , carbs and plugs aswell . You can pour oil into the rocker cover and it will gravity feed to the sump via the internal drains aswell as lube the cams/rocker arms . You could even loosen the cam chain cover and get in under it , I dont think you can fully remove it in the frame though . Even though they are a dry sump , you do get oil pooling in the sump over time sitting . So it wouldnt hurt to have a look and clean and you can check the condition of you primary chain/adjusters/oil pump . The rubbers on the adjusters for the chains can and do perish and will start to throw chunks ( not good ) . With the main oil tank , you can suck it and use a light to look in , or flush it with solvent , in or out of the frame , using the lines or just funnels . Whichever suits you , fully out is less mess though , but in with the lines attatched and into a container could work well . I do my filter dry as the F2 has a spacer plate/oil cooler supposedley and it can be a bit fiddly . I just fit it and use the starter to prime with the kill switch on . Hopefully you gas cap is just the rubber glued to the tank and not rust , if you take the fuel tap off you can upend it and use some solvent/gas to loosen . I would use the kickstart to turn your motor over . I recently saw a pic of what can go wrong when too much pressure is placed on that little nut and it`s keyway . You mention replacing o-rings , most or the rubber could be shot and this may even include the intake boots , airbox boots , cam tower pucks and a few oil seals . So any and all replacements can go a long way , oh and the torque values are very low on a lot of the engine nuts/bolts , so be gentle when doing them up , good luck

 

[ScottG]

Thanks so much for your very helpful response Hinksy! Funny you ask about the borescope. I have an articulating one arriving tonight, so I will be able to get a very clear view of the valves tomorrow and I will post them Sunday or Monday. I am planning to do a full rebuild, but it would be fun to get it running before that - even if it is down on compression.

Great tip on getting oil into the sump. I will add about a quart via the tappet cover openings and 2 quarts to the cleaned out oil tank. But first I will drop the pan and get that cleaned out as well as the screen. I will also check the chain, adjuster rubbers and oil pump.

I'm going to remove the oil tank and clean it thoroughly with solvent. The oil was pitch black, but thankfully no debris in the oil filter or in the oil from the sump or tank. I will replace the o-rings when reinstalling.

I'll heed your advice and use the kick starter once the oil is in. I have Mystery oil in the cylinders and Stabil fogger to further protect the cylinder walls. It has moved freely at the crank (with no torque applied), so I should be in good shape with the kick starter at this point. One question on the starter. My electrical wiring needs to be fully replaced - it's not in good shape. Can I just attach a remote starter button to the starter solenoid (signal terminal) and to an external battery to crank it - my battery is removed from the bike?

Also, I'm ordering a new wiring loom. Are the after market ones of decent quality, or should I pony up for a Honda NOS wiring loom?

I have ordered intake and airbox boots already - they are hard as rocks.

I will use my smaller 1/4" torque wrench for the low value bolts - thanks for the heads up.

Thanks so much for all the wonderful information - I really appreciate it!!!. Pictures coming soon

 

[dirtdigger]

The aftermarket harness seem to be fairly decent. make sure you get the correct year as there are differences. When you have the oil lines disconnected pour some oil in them and let the oil run down to the pump, it will help to prime it and make it pump oil faster. I use a pressurized oil tank to prelube my engines then you know you have oil to the right places before cranking. getting oil pressure by kicking over will take forever, if you cant prelube it I would pull the spark plugs and spin it with the starter. I have also pulled the oil gallery plug on the right side and tipped the bike on the left and fill the gallery with oil, oil gets directly to the main bearings that way. Be sure to look for oil at both ends of the camshaft when you get it running to make sure the oil orfices are not plugged.

 

[ScottG]

Thanks so much for your suggestions Dirtdigger.

So I assume you would remove the hoses at the oil tank and not at the engine. Given that the tank, sump and filter will be completely dry, how much oil should I put down the hoses and separately into the tank? I would like to get 1 quart into the sump and 2 quarts into the tank, if that sounds about right.

Also, should I split the quart between the delivery hose and the scavenge hose, or can I just put the entire quart down the delivery hose which seems to make sense since that is the return hose to the engine?

Great tip on the oil gallery. How much oil should I try to add to the gallery - given I'm already putting 1 quart down the oil lines?

Thanks again,

Scott

 

[dirtdigger]

whatever it takes to fill the hoses and the gallery, wont take a lot, basically just filling the hose itself and hopefully a bit will find its way into the pump. Really no point putting oil in the sump as it will get there from normal running, should only be maybe couple cups in the sump if the check valves work properly, if you get any substantial amount in the sump when not running then the check valve in the oil pump is not working.

 

[ScottG]

Thanks for the clarification - much appreciated.

 

[hinksy]

Yes scott , you can attatch a remote starter to it or even jump the terminals on the starter solenoide , but the remote will have less sparks And yes the aftermarket harnesses are ok . I ended up using one on mine and some of the wiring was different as in the guage . I dont know if it is a cost thing or 50 yr old wiring needed the larger guage , but the one I got and all of them it seems , have two red power wires instead of one big one . But everything fitted and after some tinkering , worked

 

[ScottG]

Yes scott , you can attatch a remote starter to it or even jump the terminals on the starter solenoide , but the remote will have less sparks And yes the aftermarket harnesses are ok . I ended up using one on mine and some of the wiring was different as in the guage . I dont know if it is a cost thing or 50 yr old wiring needed the larger guage , but the one I got and all of them it seems , have two red power wires instead of one big one . But everything fitted and after some tinkering , worked

Thanks for the very helpful update Hinksy.

So given that this bike is a high mileage bike (95K) and probably never had a top end rebuild, I will be doing a top end for sure and most likely the bottom as well.

Here are the pics from the borescope. Pistons 1 & 4 were at the bottom of the stroke so I got a pretty clear picture of the condition of the cylinder walls and valves. The walls clearly have horizontal marks, in line with the high mileage of this bike. The valves on 1 & 4 were closed, so I couldn't get a real good picture, but needless to say a valve job is in order at a minimum, given the build up on them. The 2 & 3 pistons were at the top of the stroke so no way to see much.

I didn't want to rotate the engine to see more on 2 & 3 until I get the sump pan off, clean the screen, prime the oil pump, check the chain for tolerances and look at the condition of the rubbers. Then I can finally add the new oil in and feel comfortable turning the engine over.

There is a ton to do on this bike, before pulling the engine, so I thought I would get everything else working and then have some fun on it for a few hundred miles. Obviously the compression/power will be suboptimal given the cylinder walls & valves, but it will still put a smile on my face to ride it after sitting so long

Thanks again for all your help!

 

[hinksy]

Mine werent the best either , so she got an 836

 

[ScottG]

Once i put a few miles on the existing engine, I will be heading down that 836 path as well. Should be a fun journey

Thanks again for all your help!

 

[Loki]

Useful tip priming the oil pump, after filling with oil plugs out kick start to turn over if it doesn’t prime loosen the oil filter until you get oil there then tighten up and crank till you get oil pressure.

Loki