problems starting

[Superjack44]

Hi I have a couple of questions if anyone can help I would be grateful, could anyone tell me what the correct valve clearances are for a 92 cb400sf
The clearances at the moment are No1 cyl inlet 3thou and 4.5thou ex9.5thou and 8thou No2 cyl inlet 6thou and 5thou ex 7.5thou and 7.5thou No3 cyl inlet 5thou and 6thou ex 6.5thou and 8thou no4 cyl inlet4thou and 4.5thou ex 8thou and 9thou.
I bought the bike as a non runner there was all sorts of problems with it parts missing etc but I have spent some time in renovating it repaired the wiring harness, carbs freed off and cleaned, new clocks and side panels plus a general tidy up.
I tried to start it on thursday night after re-fitting the carbs without the exhaust on and was surprised to hear it fire up quite quickly for a couple of seconds.
Friday morning re-fitted the exhaust and tried to start it again nothing,an occasional pop but that was it the starter motor is whanging it over but it sounds like there is no compression however on removing the plug on the stator side and turning it over with a socket I can feel some compression .
Can anyone explain the Ht lead layout just in case I have them on the wrong way. Jack

[ian]

I've got a 98 super four.

I did the valve clearances recently, but I worked in mm, not inches. I think they should be 0.15mm inlet, and 0.20mm exhaust side, both plus or minus 0.03mm


As for starting, I think its a fuel problem. I had something similar when balancing carbs - the tank was off ages.

When starting, the bike was turning over fast with the odd pop, but nothing. full choke also made it pop a bit.

I then primed it again directly into the fuel pipe with my bottle of petrol, and it caught straight away.

I think it's because my downwards (prime / reserve) position on the fuel tank switch doesn't work. So the fuel tap needs a vacumn to let fuel through, but the starter can't create enough vacumn to open the fuel tap = annoyance and a worn out battery.



If its not this, then you've got 3 things needed to run: fuel, air, spark. Spark is the next easiest to check.


hth

Ian

[Superjack44]

Thanks for the reply today I checked the compressions they are from as low as 90psi to 105psi as the bike has stood for a number of years I think the rings could be gummed up and was thinking of pouring some diesel down the plugholes and letting it stand overnight then trying the compressions to see if that made a difference.
I have a spark and it did make an occasional pop in the exhaust.
Do you know where I can get a head gasket if I do have to remove the head and barrels. Regards Jack

[Superjack44]

Well I finally got it running and its nearly but not quite as good as my first SF.
Temp guage is working rev counter working, things are looking up