Long time no see, so an update

[Marcarl]

10 hours ago, greg_in_london said:

I've changed the rad cap for a new after market one. It certainly holds some pressure, though I have no way of measuring exactly how much. Once it starts bubbling though, it really bubbles, more like there is a hot spot that is vaporising the coolant. I'm using a pre-mixed G12+ coolant that I think is fairly high spec.

The vapour tester kit arrived just as we were going out to get my second jab and then going shopping, so now I just need to summon up the courage to do the test.

Waiting with abated breath.

[greg_in_london]

Hopefully I haven't tried to be too clever. I took pictures and video and combined them. I had to use a rubber bung upside down to block the rad cap hole and then run a bit of hose to get round the fairing. It took some fluid out first so it wouldn't go up the tube. Later I put it back in case the surge tank was allowing a by-pass, which didn't help and I wouldn't recommend.
Basically I didn't see significant bubbling and I'm pretty sure there were no leaks around the bung - I squirted fluid and it didn't obviously bubble.
Look at the pictures and video here (it isn't too long): 

 

[Marcarl]

Just thinking out loud here. Sounds to me like that power plant may only be running on 2 or maybe 3. Way to much shaking going on.

Never mind that you had only a few bubbles, there should not be any of those,,, after all, it's not the bath for the missus is it?

If I am right on it not running on all four, then why isn't it? Could be that 1 cylinder is out and not combusting, but also leaking into the coolant. If it's not combusting, there wouldn't be any combusting gases to test for. Maybe pull the plugs and see what they look like, and do a compression or leakdown test.

[greg_in_london]

Good thought. Each cylinder is hot to the touch, but with water cooling it would do. I do think it is running on all four though - I've had a misfire before and think I remember what it's like (easy not to though - it does still run with three). The obvious way to be 100% sure is to use an infra red thermometer on each exhaust pipe, which I can do easily.

It would have sounded lumpy because of a questionable seal from the front left downpipe to the collector box, loose ones to the silencers and, most crucially, a poor seal on the rear right nasty/silly olive joint thingy. The collector box is the result of my welding - replacement bits are hard to come by and my welding never better than middling, especially when having to build sections up. The silencers, well, when they are tight, getting them off damages the collector box too much, so a loose fit until I make up some silicon rubber seals is damage limitation. That rear pipe seal though I despair of. It is just an awful design and new seals are loose almost straight away. I keep meaning to experiment with placing a feeler gauge inside the olive to take up additional space and make it tighter, but haven't done that yet.

I ordered a thermostat - £46 - about $60, but (and I didn't realise this when I placed the order) it will be on back-order from the EU and so the expected delivery date is 15-16th June 😞 My normal preferred supplier had said they couldn't get it though.

I'll let you know the results of the test on the downpipes, but it looks like the Venture will be going back into the lock-up again.

[RDawson]

There is an automotive thermostat that can interchange cheaper. Napa part # 455318. Part stores should be able to cross reference that. Way cheaper than $60. 

[saddlebum]

Its not uncommon to see a build up of pressure with the rad cap off because you are lowering the boiling point when you remove the pressure cap. Think about the times you fill a cooling system then run it without the cap usually end up with a sudden shower. That,s not to say that maybe there is not a bit too much bubbling going on there but also  not that it particularly is an issue either. With the coolant lowered and temperature rising that bubbling could just be due to expansion of both air and coolant in the rad. With the amount bubbling through the solution with out changing colour  however I would say there are no combustion gases entering the rad. The fluid is very sensitive and changes colour very easily if there is any combustion gas existing. Matter of fact we would take a breath sample with it to see if the fluid was still good.

Edited May 15, 2021 by saddlebum

[greg_in_london]

3 hours ago, RDawson said:

There is an automotive thermostat that can interchange cheaper. Napa part # 455318. Part stores should be able to cross reference that. Way cheaper than $60. 

Thanks for that - I can see that is available for pennies in the USA ($5.99) but couldn't track it down here. Most of our parts shops have been taken over by big chains who can find nothing not on their computer system (which means if I can't spot it on their website they won't be able to either). When I get the chance to ask I will though, even though I have one on order already because I don't really want to wait.

All four exhausts warm nicely as it warms up. Tiny differences in where I point the the tester give widely different temperatures (80-120 degrees, though I didn't run it for long), so I can't really say if there is any difference in how quickly they are warming, but it is definitely firing on all four.

[saddlebum]

32 minutes ago, greg_in_london said:

Thanks for that - I can see that is available for pennies in the USA ($5.99) but couldn't track it down here. Most of our parts shops have been taken over by big chains who can find nothing not on their computer system (which means if I can't spot it on their website they won't be able to either). When I get the chance to ask I will though, even though I have one on order already because I don't really want to wait.

All four exhausts warm nicely as it warms up. Tiny differences in where I point the the tester give widely different temperatures (80-120 degrees, though I didn't run it for long), so I can't really say if there is any difference in how quickly they are warming, but it is definitely firing on all four.

I like to start with a cold engine and just use my hand to see how quickly each pipe warms up initially then follow up with a temp gun.

BTW I noticed your using red or pink coolant just make sure it is not DEXCOOL which was designed for Certain GM engines. In other engines it has been known to be very unkind to head gaskets.

[cimmer]

The Napa part # 455318 is for the following cars:

Application Summary

Toyota Camry 91-83, Toyota Celica 97-90, 87-86, Toyota Corolla 97-92, 86-84, Toyota MR2 95, 86-85, Toyota Paseo 98-92, Toyota RAV4 96, Toyota Tercel 98-80, Toyota Van 89-84, Toyota Van Wagon 88

Maybe checking an auto parts store there for a thermostat for the above cars might yield you a better price.

Rick F.

[Patch]

what the heck is all this mail about rad problems and curly's?

Listening to her run is pretty sad; sounds to me like a hybrid Kawa/HD failed nightmare.

1) fabricate a T to check oil pressure (measure when cold)

2) check compression if those pass then 

3) check exhaust for obstructions ( a family of 9  pink things nesting in the collector)

4) Run the bike for 2 minutes, pull the spark wires off the plugs then measure the heat at the base of the plugs. Then repeat for 3 minute at 1/4 throttle.

5) re-shim the cams

ps don't fool around with the oil pressure test, you only need one reading, preferably with a T but the crank alone will be acceptable. Saldetramp can help you fab something together he knows where I'm going with the problem

 

[greg_in_london]

Patch - What is it that you think could be the problem ? You think that an oil problem could cause overheating like this without parts failing ? The carbs were a problem, but seem fairly good now and were balanced with decent gauges. The exhaust could be a problem and does need work, but I don't see why it would cause overheating if all pipes are a similar temperature and it runs okay on the road. Did you mean use the infra red gauge on the casing by the plugs ? Actually taking them all out takes longer than a couple of minutes, so I'm not sure what you're saying.

The cams could do with shimming - it has been a while since I got into them as access is not easy, but before I faffed with a half dozen other issues it wasn't overheating and I've done much less than a thousand miles since then, so it's hard to see that could have been such a big issue come on quickly since then.

I'm glad of every contribution and thank you for your time, but I'm trying to follow the logic and not really following your train of thought.

[greg_in_london]

Hi Cimmer,

This is the closest I've found to what you said, though EBay says it will not fit the Rav4. There is a whole bunch of equivalents, but the makers don't seem to tally across the pond. For a tenner I might just get one and see. If it doesn't fit I can just try running it without a thermostat and see what effect it has.
https://www.ebay.co.uk/itm/233914467352?fits=Car+Make%3AToyota|Model%3ACorolla&hash=item3676638418:g:CRoAAOSwqo1gPC1A

these are the cross references - I don't know if you will have heard of any of the companies over here:

Cross references

BGA	CT5491K
CALORSTAT by Vernet	141682, TH141682, TH141682J
FAI AutoParts	K20182
MAHLE	TX 7 83D
MOTAQUIP	VTK6
QUINTON HAZELL	QTH115K
UNIPART	GTS515K, GTS870K, UGCGTS515K

[Patch]

 

Hi Greg,

First I want to say you have a good mechanic already involved in the thread with Tramp. Just re read the post he wrote about the pump, that a OLD MAN that knows his stuff.

I'll fill in some comments to your questions below but first off I am only viewing it thru the eyes and ears of experience with old engines meaning not just because it is a Yamaha Venture.

                                     -----------------------------

""""Patch - What is it that you think could be the problem ? You think that an oil problem could cause overheating like this without parts failing ?""" Pressures can. What you are describing/thinking is a catastrophic failure. Something does not have to break to reach its limits. Often we see engine with sever over heating such as boil overs in a worn down engine. Sometimes this is a premature failing sometimes neglect sometimes just bad luck. We can easily tell this thru compression and oil pressure readings. I'd be looking for something around 80 pounds of oil pressure. If as I hear via your video is really happening then the journals are bleeding to quickly. Venture does not a potential problem with the oil passages clogging by the way. 

 

'''''The carbs were a problem, but seem fairly good now and were balanced with decent gauges."""" Some years back @Du-Rron had a thread where we discussed carb balancing, there are basics that are often ignored by hobbyist when starting a tune. Experience tells us when the tune is not adding up, a hobbyist is at a disadvantage there because we can cheat any carb to match the breath to the intake strokes!

 ''''''The exhaust could be a problem and does need work, but I don't see why it would cause overheating if all pipes are a similar temperature and it runs okay on the road.''''''' What I am referring to is the potential for a stuffed up system.

""""Did you mean use the infra red gauge on the casing by the plugs ? Actually taking them all out takes longer than a couple of minutes, so I'm not sure what you're saying. """" Just pull the wires, work quickly and take the readings at the steel below the insulate, that is as close to combustion real heat as you need.

""""The cams could do with shimming - it has been a while since I got into them as access is not easy, but before I faffed with a half dozen other issues it wasn't overheating and I've done much less than a thousand miles since then, so it's hard to see that could have been such a big issue come on quickly since then."""" Furthering my point.

''''I'm glad of every contribution and thank you for your time, but I'm trying to follow the logic and not really following your train of thought.'''''

You are only looking at the result as in the boiling over of the cooling system. Trouble shooting is incorporating the failing system as a result of something else "potentially"!

Look I've been wrong before however what I stepped out for you will prove it one way or the other.

best of luck