350 YPVS coolant fountain!

[petesmancave]

Hi, I'm looking for some help/inspiration.....

My F2 power valve refuses to hold onto it's water. The story goes rebuild top end, go for gentle run of 10-20 miles. Back home and re-torque the head as per the book. Next run, I get around 40-50 miles and fizz, the coolant starts pumping out the overflow bottle. Not while giving it the berries, just cruising. Not dramatically but it's leaking and by the time I get home the tick over is running rough and I have a wet left foot. So I suspect head gasket. Take it apart and as best I can tell no sign of a failure. It all looks more oily than hot. No sign of pre-ignition on the pistons....
So I go through the whole thing again. I've tried to remove any potential issues. I've cleaned all the threads out on cylinder barrel and head studs and nuts to ensure the torque goes where it should, gasket faces cleaned to spotless, head lapped flat on mirror glass, new coils and leads (Norbo's nice racy ones), Iridium plugs 

The bike has tuned barrels (Mick Abbey), KR1 carbs & pod filters, Gibsons, thick radiator, RGV 50 C thermostat with housing spacer.

I did wonder whether the extra volume of water in the big rad is overwhelming the overflow, but it doesn't explain the poor running when it's overflowing. 

My other (std tune with pipes and jetting) YPVS runs lovely. So on this tuned one I don't know whether there is a design weakness with the YPVS that needs care with the power increase from the tuning mods? I've tuned RDLC's to higher states of tune without issue.

I do see Norbo's cool heads for sale. Is the std YPVS head a weak point for a tuned motor?

Is there some other checks tests I can do to isolate the issue or some other ideas about what the cause may be?

Wade in. I'd like to be riding it more than spannering through coolant..............

Cheers Pete 
 

[rich]

Have you tried another pressure cap? Also might be worth torqueing the head to the barrels before you tighten the cylinder base nuts.

And not wishing to state the obvious but when you retorque after a run I'm assuming you let it cool right down first?

[Yogi]

Have you checked the waterpump or fitted an high flow one
Checked it's turning with the engine,just a thought ?

[yamark]

Header tank filling up is usually head gasket. The compression displaces the coolant.

I assume the rad has lost some coolant when you remove the rad cap.

Did the bike run hot?

Rich and Matt make good points to check.

Check everything carefully.

My guess is head gasket or rad cap.

HTH Mark  

[petesmancave]

Hi Mark,

I'm with you for the cap or head gasket. Cap is new Yamaha OE. I've stared at the removed gasket (this one has done maybe 60 miles so popped straight out). Ok, it's a metal one but I can see no signs of failure. I'm running a new Vapor dash which is taking the temp from the between the pump inlet and the rad lower outlet so while the temp is lower than I would expect for a boil up, it's going to be way different than from the head in the standard set up having gone through the big rad. I'm tempted to rig up the std type temp gauge to see both ends of the problem, so to speak. Either way, I've got lovely pink coolant up my leg again..............

Thanks for your ideas.

[4l04ever]

Do a leak down test too, to see if compression is pushing the water out.

[petesmancave]

Hi 4LO4ever

Have you got a good method for the leak down test?

Thanks

[JonW]

Check in the sales section of this forum, there is a kit you can grab from there.

[dusty350]

Hi
I know you said you checked cylinder studs and head bolts, but I had a problem before with coolant loss and it was down to 2 studs on the left barrel. They looked fine and seemed to torque ok but they weren't quite right. Also, are your head bolts and washers standard ?

Dusty

[stusco]

Maybe a crack?

[beardy]

does rad get hot all over? thinking blockage.

[4l04ever]

May 2, 2016 21:42:46 GMT 1 petesmancave said:

Hi 4LO4ever

Have you got a good method for the leak down test?

Thanks

You have to seal up the exhaust ports and inlets and pressurise it upto about 5 or 6psi and see if it holds pressure for a few minutes. Supposed to be more difficult with YPVS engines, as the valves may leak air too.....

[muddyfox]

a good tip for copper head gaskets is to run it without water for a bit, let it cool the retorque, then fill!
if you have a used one, you can reanneal using a heat and reuse it!

a cheap alternative for a pressure test is to get some testube rubber caps (ebay)they come in many sizes, get a one way valve with a compressor gauge(ebay) and plug the other orifices and use a bicycle pump, mine cost less than 10 dabs to make!

[bazzer5115]

Just a thought,make sure the head bolts are not bottoming out.If the head has been skimmed/re profiled a couple of times and incorrect head washers(too thin)are used,then the torque reading is the bolts bottoming out before the gasket is compressed,maybe?

[petesmancave]

Jonw thanks, I'll take a look.

[petesmancave]

Dusty350 thanks - definitely going to check the studs etc very carefully. Do you know what was wrong with yours? Studs and nuts are all standard in theory!

[petesmancave]

4LO4ever - thanks. It makes sense. I'll take a look.

[petesmancave]

Muddy fox - cheers for that. Blue Peter badge for that for sure ?. I'll have a look.

[petesmancave]

Bazzer5115 - thanks. Head has been skimmed so I'm definitely interested in that one.

[tell7437]

Is the hose from the stat going back to the radiator, does the big rad have the hose fitting ?

[Mr Kipling]

Hi there , just a few suggestions , whilst head is off make sure barrels are level with a small spirit level , also run a flat tap (non tapered ) into the barrel nuts , u can skim the head quite a fair few times before worrying about them bottoming out as long as standard washers are used , always tighten barrels first , use genuine head gasket an torque in the two stage sequence as instructed in any good manual , lastly don't over tighten when reassembling... its so easy to distort the head , best regards..

[petesmancave]

Tell7437 - yes the rad has the std connections.

[petesmancave]

May 3, 2016 23:42:42 GMT 1 Mr Kipling said:

Hi there , just a few suggestions , whilst head is off make sure barrels are level with a small spirit level , also run a flat tap (non tapered ) into the barrel nuts , u can skim the head quite a fair few times before worrying about them bottoming out as long as standard washers are used , always tighten barrels first , use genuine head gasket an torque in the two stage sequence as instructed in any good manual , lastly don't over tighten when reassembling... its so easy to distort the head , best regards..

Hi Tig, sound advice all. I'd checked the barrels all seems level and true. I'd tapped the nuts for head and barrels for good measure before plus run a die down all the studs to ensure the torque was going where it should. I bench assembled the barrels and head yesterday and there appears to be several millimeters of space before studs and nuts bottom out. I do follow the 2 stage tightening sequence. I guess the one that I've not been religious about is OE head gasket. I've used Norbo's best quality ones instead. I have used up all I had so a trip to Tamara us perhaps on the cards. Thanks for your thoughts. Much appreciated. I'm going to play around with a leak down test,  although I'm tempted to seal up and pressurise the coolant circuit on the head/barrel assembly just to see if anything obvious cones to light.

[kostas]

Go for the OEM gasket.. I did and solved the problem...

(Problem was that the overflow pissed in my face at 170 klm/hr)

Kostas

[petesmancave]

May 5, 2016 18:55:47 GMT 1 kostas said:

Go for the OEM gasket.. I did and solved the problem...

(Problem was that the overflow pissed in my face at 170 klm/hr)

Kostas

Hi Kostas, I here ya ?. Thanks.

[Mr Kipling]

Cant go wrong with genuine head gasket , its always tempting to use pattern , but in tuned engines , blow regularly , if your feeling flush , a wicked cool head either from Norbo or Martin at MBD work wonders...

[petesmancave]

May 6, 2016 1:13:44 GMT 1 Mr Kipling said:

Cant go wrong with genuine head gasket , its always tempting to use pattern , but in tuned engines , blow regularly , if your feeling flush , a wicked cool head either from Norbo or Martin at MBD work wonders...

Thanks Tig. OE gasket on order ☺ for now..........