oil pump non return valve

[guest668]

have had on going problems with heavily smoking and oil using srx400 tends to be worse on acceleration and it was suggested to me was probably valves...have taken head off and though valves have heavy carbon deposits on them they look ok and not much wear as does the piston...engine is avout 30,000 miles. 
another suggestion was made to me to check non return valve in oil pump as this can fail and therefore cause drain on engine oil and cause heavy smoking...has anyone else had experience of this or think this might be a possibility?

how do i go about checking it is it easy to repair or best replaced etc etc.

[themoudie]

Aye beezer764,

Are the valve seals on top of the guides OK? Not cheap to replace with genuine parts, but had problems with pattern ones 'popping off'! Resulting build up of carbon eventually resulted in engine only rotating 355 degrees instead of 360!  Top end rebuild.

Seals in oil pump age and require an engine strip and build, plus a new pump (£90 odd notes from friendly Yamaha dealer, again!), or else strip and machine pump body to accept 'standard' sized seals, rather than 'one off' size fitted by Yamaha and 'unobtainium'! 

I suspect the first and also the easier to undertake.

SteveL, SteveH, ian650 and Andy230 may all be along to impart their own thoughts, guesses. May I wish you luck.

If you need a manual, make a donation to the Rob Vine memorial fund and I'll be pleased to trust you and despatch, as an email attachment, a copy.
Parts lists etc on SteveH site 'SteveH_site'

All the best, Bill.

[Ian]

I think Bill has covered probably all the probable causes in his usual exemplory fashion.

Im still thinking of anything else, and Im sure someone will come along with the "unobvious obvious"

Good luck but these engines are pretty tough cookies if looked after and treated properly

Ian

[Steve Lake]

I'm going for the valve stem seals first, worn bore/rings second, valve guides third.

smoking won't be caused by the pump or seals, but can be the cause of accelerated bore wear if it's not providing enough pressure....I have found that this is usually caused by scoring on the pump lobes....not the seals...but the costs are the same...new pump 90 quid plus., but money well spent to my mind, i always replace the pump on any engine i don't know the history of, lot cheaper than rebore/new piston/rings.

the oil non return valve won't cause smoking either (well, if it has failed big time i guess you could get smoking until the pump has scavanged the sump... say 5 or 10 mins)... if the non return valve has failed and allowing 'wet sumping' you should see a slow migration of oil from the tank to the sump...i.e. the level in the tank will fall over a period of time...but this will be very slow.

you can get the ball/spring/seal from yamaha, not too pricey...see SteveH's srx600 website. the non return valve parts are the same on the 400 and the 600.

[Steve H]

Must admit I always thought if it smoked on deceleration or gear changes then the valve guide seals were leaking, smoking on acceleration was rings.
How much oil is it drinking ?.
Does it smoke noticeably when you start it from cold, and then clear  ?. If so then valve guide seals.

[guest668]

hi thanks for all your thoughts...it smokes heavily on start up and from memory did clear up a bit over distance. though smoke doesnt look blue and i alays thought blue smoke meant valves...just before i took  it off the road i was having to top up the oil frequently.

[Steve H]

If it smokes from a cold start, then its most probably valve guide seals. Whilst its standing the oil runs down the valve guides into the port, this then burns when you start the engine, hence the smoke.

[guest668]

how do i go about checking the valve guide oil seals to see if here ok? any ideas

[Steve Lake]

strip off the head (can be done 'in-situ') then remove the springs, you can then see the valve seals, they usually go hard,
if you withdraw the valves, the cap on the valve will bu55er up the seal as you pull it through....due to burrs on the cap caused by the collets.
so any which way, you'll be replacing the seals....so get a gasket set in (not sure where you get a 400 gasket set from) or a set of genuine seals from yamaha (same as 600 ones, so see SteveH's site for part numbers)
at least you can then inspect the bore and valve seats etc