Topic: 1978 CB750K7 Its going to be a Journey

[shorterdanny]

Well

Having joined this site last a couple  of weeks ago, and with the bike sitting lingering in the garage i thought i should finally get round to playing with her!!!!!

After going for a spin it was clear something was wrong!!!

Did the touching the exhaust test.....and yep only 3 of the four cylinders were firing.....No 2 cold.

Have spent the last week dreading what might be wrong, but simple enough, for some reason the plug had stopped working, electrics all find. For good measure replaced all four and now back to four cylinders.

Thats job 1 done, so anyway now i have a start point.

Plan for the bike is not yet clear, love the Cafe look, and that was the initial plan, but since join this site i have seen some super cool looking bikes, that are a mix of the endurance,flat track,cafe look so going to keep looking on that front.

First thing is just to get her running sweet, currently have lots of bits on the way,

electronic ignition
Dyna 5 Ohm coils
Dyna ignition leads

as well as all the normal list of service items, engine flush, oil filter etc etc.

The next major job is stripping the carbs down, as there is a significant hesitation on the pick up, and a rough idle, so think the pilot jetsd are clogged. we'll see. 

picture 1 she bit back, burntwrist on the exhaust stupid, not the first or the last.
picture 2 my home made petrol tank works a treat,much easier to do things with the tank off.

[shorterdanny]

Hi all,
Why is it that when my motivation to hit the garage is all go, that work ramps up and i can’t get 5 minutes to myself let alone time in the garage.
Still have been trying to use my time wisely, work internet has take the hit, as have been spending my time reading as much as I can from this and other forums and trying to decide exactly what order things are best done in. Anybody else find the more they read the more confused they get.
Came to a conclusion though, take 2 feet and jump in!!
My limited mechanical knowledge, keeps scaring me off jobs, well not today
So far today have
1.   Adjusted the valve clearances
2.   Adjusted the cam chain
3.   Removed the exhaust
4.   Removed the Carbs
5.   Started stripping and cleaning the Carbs.
Carb findings.
1.   Only have 112.5 Main jets installed, now correct me if I am wrong but the CB750k7 had 115 jets as standard. Now with the 4 into 1 exhaust and the pod air filters the main jet size should be larger than standard not smaller.
2.   Not that gunked up in the float bowl, all looks fairly clean, to the point i think they might have recently been cleaned.
Next job, clean up all the carbs and links, fit new 120 main jets refit carbs and see how see runs! Hopefully the larger main jets will solve the hesitation issue at high throttle settings.
Once thats done flush the engine, fit the new electronic ignition check all runs ok, then the real fun can start. Ripe it apart and start the redesign.
Questions
1.   Does anyone know any good suppliers of Keihin Jets in the UK, save a penny or 2 on postage from US?
2.   How do i get pictures in the test rather than attaching them at the end of the post?
3.   Does anyone elses text box default to the top after every key stroke, gets hard to type when screen stays at the top and you can;t  see what you are typing.

[traveler]

Welcome mate!

More pics is always a good thing!

Can't help with parts in the UK.....the shipping costs, taxation and such are going to be a real downer.  Get with Sam on here!

~Joe

[shorterdanny]

pictures

[traveler]

some of your metal bits appear to have a little bit of English residue on them from that nice damp air (RUST).

oh well...more scrubbing you!

~Joe

[shorterdanny]

it adds character 

but have read you project thread so i am expecting the sore fingers.....

but this is going to be a riding bike so never going to be picture perfect.

am loving this bike out of the bike of the month thread, might be heading in a cross this with cafe look.....

[shorterdanny]

New #120 main jets arrived today, hopefully get the carbs cleaned and refitted on thursday ready for a weekend blast...fingers crossed..only cost £10 for the 4 so not sure about the quality but we'll see....

[shorterdanny]

Well before i stripped the carbs it was running on all 4 cylinders with only issues at the top end,

Now having removed the float bowls and replaced the main jets and generally cleaned the bottom area she runs well on Cylinders 1 and 2 however 3 and 4 appear to fire now and again, exhausts only warm up a little compared to 1 and 2.

I did take them off the rank and clean it up a little, and using new rings to seal the rubber mounts.

not really sure what the prob is at the mo, did spray some wd40 around the mount areas and didn't see any bubbles, but going to pull them off again tomorrow and start again..

people say these carb things are a night mare well yep i now agree.

[shorterdanny]

Update

put the problem mainly down to the carb insulators not sealing thus losing vacuum....
so with  a hair dryer, rubber mallet, brut force and ignorance worked quite well, then i got the biggest screw driver i had and really worked the insulator rings as tight as possible, now all sealed nicely and runs well.

also i have no centre stand, so with the bike leaning over the fuel from my rigged up fuel tank, wasn;t fill the bowls enough, thus bike would only start with the choke on full and on full throttle, straight to main jets which are longer than the pilot jets. once i did the float test with clear tubes i realised this and raised the fuel tank to get a bit more pressure and hay presto float bowls full started on the button and now idles at about 1500 rpm which after no adjustment since my carb clean i though was pretty good.

[shorterdanny]

Update

got 2 deliveries today. one package contained a po15 tank repair kit, and the other new tappet inspection covers, and new grips lovely.

also managed to get a wee bit done, have sorted my workstation ou so have a nice place to work, and fitted a new set of handle bars, managed to get them for £4 from a auto jumble at the weekend, not as nice as propper clubmans but fitted them upside down and should work quite well, have also started to restore the inside of my tank.

Tomorrow i am going to start looking at the seat and front and rear mudguards, once they are done the basic outline of the bike will be done and i can then start stripping and cleaning everything. the fun part.....(overall theme for the bike is a simple cafe racer look, with the electrics minimised and hidden where possible and a custom oil tank to open up the rear triangle. I know it has been done before but i haven;t really seem any around where i live. then i can just add loads of custom bits and keep tinkering.

a few pictures below.

[shorterdanny]

more pictures