Valve springs?

[nxp]

Tonight I did the valve lash adjustment on my 121, (old model, carbed 8-valve, 4spd) I set them all to 0.30-0.33 and she started fine after. What really worried me was the unbeleivably soft valve springs. While unlocking the locknut on the adjusters the least pressure would depress the rocker, compress the spring and open the valve partially with not that much force.

Is this normal? I've seen much stiffer springs on practically everything, from motor scooters to cars so I'm having nightmares of valve float at 4000rpm and thinking that my wussy engine is a wussy just because of the bad valve action. Am I making a fuss about nothing or are the springs normally very stiff and I've really got something wrong?

Btw, mileage is unknown and it is very improbable that the springs were ever replaced.

N

[jglutz]

I've never been able to easily compress a valve spring ny hand....your description seems really soft.
Soft valve springs will create a loud valve train and/or alot of puttering in the exhaust....also, the idlel/running vacuum will be low.
Do you have a shop manual that list the srpring rate...the number will be in units of...lbs/in...or...oz/in...or...N/mm?

[nxp]

Unfortunately no manual.... I've got just the electronic version for the more modern 16valve singlecam 121 and it's useful only in places which didn't change much.

She does happen to have a slight stumble which goes off at a particular throttle opening (changes with speed/engine rpm), and it was much worse until I put in a thermostat (some cheapskate previous owner just threw it away when it failed), but it's still there to a ;esser exent. I'm suspecting it may be a carburetion and timing issue, but from what you say the weak springs could be throwing everything off by a bit. Power drops off drastically at higher revs, and even a 1litre swift feels nippier t high revs.

Does anyone who has a manual care to check the spring rates for me? (I'm not really in the mood for pulling the head to replace the springs just to find out it was something else!)

[geezerstiva]

i've got this manual. but i'm at school right now. i'll check it when i get home and post them tomorrow.

[jglutz]

Sounds like time for a complete tune up....not that hard...not much $$$$....alll easy stuff.
Wouldn't hurt to do a compression and vacuum test...will show if the valves are mis-behaving.

[geezerstiva]

ok, didnt see anything about spring rates, but i did find this. it said if the valve seat is too wornit will make the springs too loose-which makes sense. says with the valve touching the valve seat and the springs off it should measure 1.52-1.54 in. from where the spring touches the head to the end of the valve stem. good luck on that one.

[jglutz]

^^That's a typical spec. Requires the head to be out or the rockers to be out and compressed air to be injected thru the spark plug port to take a measurement. This spec is usually checked after grinding. In any case that's alot of seat wear to produce a lose spring?!?!?!?!

[geezerstiva]

yeah, but it said that if it was that worn you could put a shim in the seat and tighten it up. but i'm with you, if youve got that much wear, its probably time for a new head.

[nxp]

Hmm... thanks for the info guys, now I'll think it over and see if it's worth repairing. I got this car just as a winter banger for when it's not beautiful motorbike weather, so not planning of investing much time and money on her (pulling the head will take quite a bit more than a couple of hours parked in the street and a few euros). She's already running much better than when I got her.... might satisfy myself for the moment.