carb synch

[ogre]

hi all nearly finished my resto of my cb750 1970 will post piccies when done been doin it for 2 years on and off an hour here and there got to keep everybody happy. anyway got engine runnin synched the carbs got good tickover at 900 rpm no black smoke but the plugs are black. does it need a run for a proper check its not quite finished to do that at mo. the air screws are out about 1 1/8 turns when its warmed up and i blip the throttle it hesitates so i thought it was the throttle cables which needed setting i did set them before i put airbox on and ran it. so according to manual open the throttle and read the gauges and adjust. on 1 and 4 carbs the vacuum dropped on the gauges dropped reading more vacuum as soon as i opened throttle. 2 and 3 carbs went slightly up on gauges but it seemed to rev a lot better than when  adjusted 1 and 4 to go slightly up on gauges the same as 2 and 3. it really hesitated cant get 2 and 3 to drop like 1 and 4 no adjustment left on carbs is the engine to hot or is there summat i,m missing the throttle cable is new 1 to 4 cable type any help would be appreciated.     

[Bitsa (Ralph Wright - RIP)]

Hi
Are we talking k0?If so what little knowledge I have is what I have read.Others I am sure will correct me but I would start off with tickover screws get them all in spec with the guages then with throttle just open tighten cruise screw on rh switch then adjust all the tops of carbs of slack.Loosen off cruise then open a wee bit and see if vacuum guages rise the same.
Cheers
Bitsa

[ogre]

yes its a k0 i take it you mean the little screw underneath the switch i did set throttle screws got the gauges spot on 21 cmhg ticks over ok at 900 rpm i also set 1 and 4 carbs to middle carbs but was worse on hesitating when i opened throttle

[ka-ja]

Hi,
     Have you synced. the opening start point of the 4 carbs.  to the throttle pull?----Ken

[LesterPiglet]

I've never heard of such a low idle.
When I do mine I always set the idle a little high, maybe 13 or 14. I've no idea as I've no tacho. I also ignore the numbers on the vacuum guages but get all cylinders as even as possible. After that is done then I turn the idle adjustment screw to achieve a satisfactory idle, still ignoring numbers.
I believe these bikes are meant to run rich at idle so you are best doing a plug chop out on the road.

[ogre]

i think so had another go today got it warmed up checked timing with strobe light inconclusive could hardly see the marks put it down to being very old and could be a bit of vibration it definitely advanced when i revved it this time though i put a fan at front of bike which seemed to help didnt hesitate as much i synched it again as i just started to open throttle and i have had to set 1 and 4 to 2 and 3 there is a bit of play in the carbs but not a lot possible bigger problem now noticed a very small oil leak coming from head gasket  talk about gutted checked the 4 head nuts you can get to next to spark plugs and werent tight torqued all the head bolts up twice on the rebuild can't believe it which i have tightened up but worried now about the ones i can't get to without stripping the engine again whats your thoughts on this can't believe for all the ground breaking design honda put into the engine for its day they never thought about being able to work on the engine in the frame

[Bryanj]

It was supposed to be 100,000 mile reliability(IF SERVICED PROPERLY) so why would you need to work on it

[ogre]

didn't know that but ford say my ford focus tdci estate will average 56mpg its never seen it they also say theres no problem with the dpf on them but we know that isnt true dont we unless you boot it every where and you live on the motorway

[SteveD CB500K0]

My FF 1.6 TDCi does 59mpg average when I drive it to the other end of the country on the motorway (at 70 mph)

I've tried to get it up to 60 mpg but never quite got there.

Normal use = 45-49 mpg...

[ogre]

urban 49mpg extra urban 74mpg combined 63mpg do a lot of miles on motorway thru work tried tickling it everywhere even neutral down hills my best combined was 51 mines an 09 had a bit of banter with my mate at work whos got a 56 to be fair he got better than me his best was 53 dont get me wrong its not bad just not quite what they spec it at but there all the same anyway im just gutted i may have to take the engine out again on my k0 

[SteveD CB500K0]

Hijack Apology:   TDCi - you can't get much further from "carb sync"...

Sorry.

[ogre]

ran the bike again yesterday there still is a very small oil leak on head gasket  put in tesco 15-40 diesel mineral oil in it as advised on here to be honest when its warm the oil seems pretty thin i put the new head gasket on dry with no sealant on or the pucks and o rings. with the front nuts which are next to the spark plugs loosening abit could get 1/2 a turn on them im abit worried about the ones you cant get to anyone got any advice or do you think its an engine out job
thanks

[hairygit]

Hate to say it, but to do it properly is engine out time Get yourself another head gasket, as it may continue weeping even after torqueing up if it's been run for any amount of time. Bite the bullet and buy a genuine head gasket if it does need replacing, safest option to avoid future hassles

[K2-K6]

I'd go along with hairygit on this one. You already have your own suspicions about the status of the unseen studs so I can see only the logical path of a strip of the head to get it right.

As to the sealant use, I've always used blue hylomar on these (I know that is not entirely agreed with, so you have to make up your own mind) and always the absolute smallest amount needed to coat the surface so that it has the appearance of something like sellotape, i.e. absolutely no surplus that could be squeezed out. UKPete has recently used a spray version to get a very thin coat with good results.

I know it's generally avoided to want to remove the engine, but it is I think easier than most people remember and worth the time to get it leak free.

[ogre]

thanks for replies should have read the forum before i built up the engine on all the previous engines i have rebuilt i have always used hylomar i swear by it but never on a head gasket its the re torqueing i never took into account cos ive always retorqued the engines without even thinkin about it i just dont wanna scratch and mark anything after all the hard work ive put into it