Hello sohc forum, Im Mark senior from northern ontario and my son Marc junior and I have a 1977 honda 750 F supersport. (this bike is rare and in great condition) I owned it and passed it on to Marc Jr.. To date it has been stored for 17 yrs broken down in my closet and garage until this past winter when Marc resurrected the old girl and rebuilt the engine with a buddy of his.
I have some questions that we really really need answered and would really really appreciate any and all suggestions:
1. The bike would only run on 3 cylinders, rebuilt the carbs with new floats and float needles, ran on three and way too rich, rebuilt the carbs again and blew them out with compressed air, #3 was cold then worked and its running on all four now. No question here as we got it running on 4 (was the carbs, they needed to be blown out)
2. The second and most important one is that the timing is retarded to the point where the 1-4 is just slightly ahead of the outside
timing mark.
factory timing marks on the base plate advance unit look like this below.
I I 1-4 II (advance)
T F
this is what I'm seeing thru the hole using the timing light at 1100 rpm - I'm assuming its retarded and not advanced.
I outside mark
I I
T F 1-4 II (advance)
it should look like this at idle 900 -1100 rpm
I (outside mark)
I I
T F 1-4 I I (advance)
at 2500 hundred it should look like this:
I (outside mark)
I I
T F 1-4 I I 23.5-25 degrees advanced
the timing should be at the F mark when idling and when revved to 2500 the advance should move forward to between 23 and 25 degrees of advance, the marks are there. the timing plate cannot be moved forward any more. the screws are at the end of the half moon slot. I can move it back and retard the timing to kill but cannot move it up to match the marks, therefore it runs lumpy and the timing is definitely out.
3. where do you find the settings for the carb floats? so far i cannot find any base setting, i did see some sort of gauge for sale on the internet but can't find it again.
Also, if i screw the airjet out it should lean the mixture and brown up the plugs. At least thats what i surmise, screw out - more air, leaner condition. IS THIS CORRECT?
4. Manual says that to tune the carbs and the timing correctly that number 2, the pump carb, should be set with a tachometer and that the airscrew should be screwed in until the bike dies then back out until the revs and the timing are correct. then check the advance at 2500 and the advance marks should line up.
bike runs but lumpy. timing plate cannot move excerpt to retard the engine not advance it,
if the #2 carb is tach set will that affect the timing?
?
5. The cam is supposed to line up with the cam seat split and the cam notch at 12 oclock high when the T - timing mark on the crank is on the outside mark. The cam does not sit exactly at 12 oclock on the T mark, it sits exactly at 12 oclock when the crank is exactly between the T and F mark. to set it exactly at the T mark the cam appears to be 2 or 3 degrees forward and the lines are not at 90 degrees they are at 93 degrees - slightly forward. Is this an issue, is the cam out one tooth?
cam notch at 12 oclock
_ * _ (cam seat split)
what tach would we use? it says in the manual the bike tach is not precise enough.
MORE TO COME, we will include pictures in the next post.
Please supply any and all suggestions here and if necessary send them to
pedrobighead@sympatico.ca
thanks
and ride on.
Looking forward to your help and great to be in the forum.
Our stable
- 2002 honda 600 f4I, k and n's and a jardine exhaust.
- 1977 honda 750 F supersport, k and n's and a hindle stealth - full header
- 2 X honda 230 F dirt bikes
- 2006 suzuki RM 250 motocrosser
- 2012 yamaha 600 fzr
- 2007 arctic cat 400 4 x 4 for hunting.
- 2012 dodge ram 1500 hemi, for hauling our stuff around.
