So im trying to keep and do as much of the work on my 75 750f as possible to help keep cost down and stay with my budget. What's the steps and tools I need to do a valve job like the gaskets and redoing the edges for the valve seats its something I want to do along with the other engine gaskets while I have the engine out of frame "the bike is still in one piece" I haven't dove into her yet but my son keeps asking when we will start working on his motorcycle "this this all coming from a 3yr old" you should see how enthusiastic he is to work on his electric quad
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Honestly you would be money ahead to send it off an have a valve job done. If guides are worn they have to be replaced first because the guide is used to center the tooling for the valve seat cutting. Then a pilot that fits the guide along with the necessary cutters for the guide angles. Valves will have to be measure to see if they are worn and if they are usable. If they are usable they would need the valve face ground on a machine. The head should be checked to make sure it is flat and surfaced if needed. You can send your head to Cycle Xchange for a basic unassemble rebuild for $325 or $399 assembled according to there website.http://www.cyclexchange.net/Machine Work & Services.htm More I would think if it needs valves. I dont like my local car machine shops so I send my machine work to Cycle X or Ape. You could take the head off and see if it actually needs a valve job or not before deciding. Does it run good? Leak oil?
Well I got it for free was told it ran last time it was registered x amount of years ago it had been sitting outside in our lovely new England weather so I yarded the carbs out and rebuilt them now I need to change the oil plugs fuel lines fuses the simple stuff new throttle cables and air filters etc them im going to try to start it
Something to think about...there is a kit that makes it so you can pull the top end apart in frame. You cut the two tubes that are above the valve cover and you weld in the remove able tube kit. If you are going to have the bike stripped to the frame then this is a worth while mod to do because then you can remove the head, cylinder, etc with the motor still in the frame. Then you can easily add cam, bigger bore etc at a later time when the stock power ends up not being enough. There are called 750 frame splice kits or Gordon frame kits. In my opinion worth the time and money if you are going to hold onto the bike and maybe want to add performance stuff later on. Other wise you have to pull the motor to do anything to it.
A ported head with bigger valves and a good cam and carbs really wake up an 836. Just sayin.
grepper
Old Bike Nerd
IMO, you should do a compression test, maybe a leak down test before you start ripping the engine apart. You might find the engine to be in OK shape. If you do end up ripping the engine apart, you might not need a full valve job, just a good lapping. Have a machinist look at it first. A machinist you trust of course, one that's not going to tell you you need a bunch of work done you don't need.
Thanks guys for all the help maybe I will do a compression test and leak test once im at that point I still have a lot more questions that I will be posting about. Maybe see you there also lol. My wife always asks me if im married to her or that damn heap of a bike out in the garage I asks her what her favorite word is and she says "no" and I say maybe im better off with the bike lol. But all kidding aside she understands bike are my passion so she is pretty tolerant.
grepper
Old Bike Nerd
Yeah, lapping is about $20, for lapping compound and the tool.
cyclebuster
CB750 Addict
cb750 valves are paper faced. very thin layer of hardness. excersize caution if your going to do a valve job. No machine grinding. you will end up with a tulip. hand lapping only. Or just buy new valves they are reasonable still.
cyclebuster
CB750 Addict
right it simply matches the faces.
I've seen a few videos on YouTube of valve lapping a few on cb750 motors. So when doing the lapping I would think it is as much by sound as it is by feel with tool when the gritty grinding noise goes away adjust tool and compound and continue. Please correct me if im wrong
Lapping wont take care of pitting, worn seats, warped seats and valves. Also if the contact between the seat and the valve face is too wide other problems can occur. There is such thing as to wide of a contact area. Lapping isnt meant to take care of leaking valves, it is to establish an initial seating of the valve and seat after a valve seat cut or new valves. Most machine shops I know of dont even lap valves after a valve job is done. If there is a problem with the seat or the valve lapping may make it seal for a while but if the seat and/or valves are worn it needs to be fixed correctly. Lapping is not a cure for leaking or worn valves or seats. I'm sure someone will say they did it and it worked fine, it probably did, it probably also didn't need it in the first place.
cyclebuster
CB750 Addict
yes that is true, but if your valve is "pitted, worn or warped" it needs to be replaced. And honestly heads dont sell for nothing normally. I have seen tons of good heads no sale at $20. If your say re ringing, replacing the head gasket, lapping will provide a new seal face. BUT if there is a valve "problem" its not gonna help.
