Warming up on the side stand....good or bad?

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8541Hawk
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Warming up on the side stand....good or bad?

Post by 8541Hawk »

So there has been a some people who have said it is bad to start a VTR while on the side stand.

This has gone back and forth many times and has also been linked to ACCT failure.
There has been lots of speculation on if it is true or not and what if anything is actually happening.

One of the things I have looked at while inspecting the cases of the engine I have torn down is the cooling system.
I have found a couple things that I would call VTR specific as its a bit different that a lot of bikes.
I will also say that I also went into all of this with the attitude of only 2 things will cause a tempered steel spring to fail. It reaches its cycle limit or something damages the temper.

With that lead in we get to, why in my opinion, it is bad to start a VTR on the side stand.

First we need to define a basic term in cooling systems, that is "The Water Table".
In simple terms it means that water will find its own level and for that reason you must mount the radiators higher than the highest part of the engine system to insure the engine stays full of coolant.
The more radiator volume and\or the higher it is mounted determines extra pressure you have to make sure the engine stays full.

Why this is something to keep in mind is the side mounted radiators.

So what happens on this bike?

You come home and park the bike on the side stand. You have now just put the left rad lower than the engine. That means the pressure for the water table keeping the engine full while it cools has been cut in half.
Not that big of a deal though a bit worse on a bike with a poorly maintained cooling system.

Now another VTR thing is you have 2 great big heads. As the system cools and every thing contracts is would be very easy , again in my opinion, by looking at the passages in the head to get a "pressure lock" from coolant turning to steam in the right corner of each head.
On bikes with longer than stock rear shock (lean farther on the stand) the issue could be worse.

So now the bike is cold. I'll cover what I think happens if you leave it on the side stand first.

On start up, again you have 1\2 of the water table pressure that the system was designed to run with.
So coolant starts to flow. On this engine there is a large passage in the center on the 'V" that feeds into the bottom of each cylinder.
Then it flows up to the heads and out the hose fittings under the carbs.

All good, what could go wrong? Well that "pressure lock" in the side of the head doesn't fill. Remember it started out as steam so it is at above atm pressure.
Plus it is at the highest point of the engine so the hardest to fill.
As the engine warms that spot starts heating rapidly. The hotter it gets the higher the pressure needed to fill the space.


But the pressure in the system will build up and just force coolant in the passage no problem.


Well you would think so but another VTR variable we must take into consideration is the carb heat lines.
They are flowing on warm up and any pressure build up will take the path of least resistance I would think.

So you running with 1\2 the water table pressure the system is designed to operate with along with the carb heat lines limiting pressure and the thermostat opens.
Now you cut the carb heat lines and you get full pressure through the block. Yes the engine completely fills and the spot the was cooking and throwing heat who knows where now gets cooled very rapidly.

Doesn't sound like it would be too good for an engine with any type of tensioner but what else could rapidly heating the the head and then hitting it with full coolant flow cause issues with?

Could this heating and cooling eventually damage the temper of the spring in a auto tensioner?

Could it also be that the reason the rear auto tensioner lives longer might be because it is filled with oil?
Many have though the oil was lubing something but actually it is acting as a heat sink.
Because the rear tensioner is full of oil it does not heat up quickly and also it does not rapidly cool. You know, what is needed to damage the temper in spring steel. :angel:

Again this is just what I see.

Now instead you sit on the bike and then fire it up.
First, at start up, you have the water table pressure the system was designed to run with.
This makes it much easier to make sure the engine is full as opposed to making sure the left rad is full like when leaned over.

Then you also move the possible "pressure pocket" to the center of the head which is now the highest point in the system.
With the way the coolant flows up around the cyl. this places it where it would be hit from all sides evenly and must be forced out in order for the coolant to exit the head.

Could it also be that the race bikes never had an issue because they don't have a side stand?



Again this is just the opinion of some guy in his shed and do whichever you like but I do truly believe you will have a much happier, longer lived bike if you simple just stand the bike up.
They don't need to warm for more than a min. at most, usually 30 sec or so. Then light throttle for a few miles until the temp gauge starts to move (well on the old analog clocks) and you're good to go. :thumbup:
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fabiostar
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Re: Warming up on the side stand....good or bad?

Post by fabiostar »

good point about race bikes never warming up on a side stand :thumbup: im not one for letting them sit on a side stand warming up but iv never done that regardless of make of bike, fire it up then sit on it while i put my helmet and gloves on is my normal routine.

now for right or wrong but its doing mine no harm so far, iv removed my thermostat, (it not gona stick if its not in my engine) and iv bypased my carb heaters aswell.. cooler carbs means cooler fuel charge and the icing up problems iv never had.....
the older i get,the faster i was :lol:
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podman
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Re: Warming up on the side stand....good or bad?

Post by podman »

Ruddy hell I thought my KR1 was the most delicate, highly strung thing I owned but im now getting anxious about the Firestorm...
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kenmoore
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Re: Warming up on the side stand....good or bad?

Post by kenmoore »

Very interesting theory.

I have never been one to sit a bike idling for warm up , I prefer to start the bike whilst sitting on it, warm it for a few seconds and then ride.

I also have no thermostat and an electric water pump but that is academic as I have manuals.

Maybe a poll of which tensioner failed from the unlucky folks that have experienced a failure would add some credence to your theory .

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Cadbury64
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Re: Warming up on the side stand....good or bad?

Post by Cadbury64 »

I'd make the following comments about the original post.

Firstly, the cooling system is designed to stay full at all times, and there are pathways for air to migrate to the highest point which is the radiator cap. It is no mistake that these are invariably located on the high side when the bike is on the side stand. IIRC, the suggested air purging method in the service manual is to blip the engine on the sidestand with the cap off, and continue to fill the radiator until the level stays constant. Revving speeds up the flow rate of the coolant and would help to displace any remaining air bubbles, and I can imagine that any time the bike is revved out in normal riding operation the coolant passages would be fully flushed. Air that is displaced would accumulate under the radiator cap, and as the system heats that would be pushed out to the reservoir and out of the system.

It seems very unlikely to me that you would end up with any "pressure locks" in the heads, unless there were blockages in the coolant passages that prevented air being purged properly. I can envisage localised boiling occurring if the coolant overheated and/or the cap fails to hold pressure, and that would create some steam, but steam created in this way is nothing but water vapour, and that will condense right back to 100% liquid when it cools, so you won't end up with any trapped air.

When I looked at the title in this thread I assumed it was going to make some reference to bad oil flow on the sidestand affecting things like cam bearings. My recollection is that some in-line fours suffered from this due to low oil pressure when idling, and the effect of gravity on the oil flow to the top-most part of the engine. I can't imagine that would be an issue for a V-twin, or a v-four.

When I bought my VTR, I installed MCCTs within a few weeks, having read the tales of impending engine doom on sites like this, and I'm sure I sleep/ride happier having done that. It is certainly interesting that the front head is more prone to fail than the back, and given they are mechanically identical the different fail rate must be due to orientation/location. The front tensioner is pushing down on the chain run, the back tensioner is pushing up, so the chain load may well be a little different due to gravity, with more tension fluctuation on the front? The front tensioner also lives in a hotter environment with more limited airflow at idle.
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tony.mon
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Re: Warming up on the side stand....good or bad?

Post by tony.mon »

One thing about your argument is that the engine, as it cools, doesn't drain any coolant out, leaving an air gap- it's a sealed system, and it pulls coolant in and out as it cools and heats up to and from the reservoir. So there shouldn't be an air gap or void that exists at any time, running or not.

To prove this, have a look in the neck of the right rad filler with the cap off. There isn't a large air gap as it cools.

However, I can't explain the phenomenon where the coolant level drops as you rev the engine- the volume of the system doesn't change, so I don't understand where that amount of coolant goes. I find it useful, though, I hold the throttle open as I top up the rads, pout then cap on and let it drop back to idle.

Anyone got a theory about that one? :think:
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VTRDark
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Re: Warming up on the side stand....good or bad?

Post by VTRDark »

However, I can't explain the phenomenon where the coolant level drops as you rev the engine- the volume of the system doesn't change
Could that be more temperature related and the molocules getting closer together therefore reducing the volume. As you rev the coolant flowing past the cylinders is getting hit my some immense heat.
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Cadbury64
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Re: Warming up on the side stand....good or bad?

Post by Cadbury64 »

tony.mon wrote: Tue Jan 30, 2018 9:33 pm One thing about your argument is that the engine, as it cools, doesn't drain any coolant out, leaving an air gap- it's a sealed system, and it pulls coolant in and out as it cools and heats up to and from the reservoir. So there shouldn't be an air gap or void that exists at any time, running or not.

To prove this, have a look in the neck of the right rad filler with the cap off. There isn't a large air gap as it cools.

However, I can't explain the phenomenon where the coolant level drops as you rev the engine- the volume of the system doesn't change, so I don't understand where that amount of coolant goes. I find it useful, though, I hold the throttle open as I top up the rads, pout then cap on and let it drop back to idle.

Anyone got a theory about that one? :think:


My thought is that the faster pump flow pressurises the hoses feeding the engine which stretch a little due to back pressure, and the flow rate through the heads/thermostat/rads is insufficient to keep up so the level at the filler neck drops. From my own observations the effect is very rev dependent. When we do the radiator fill the thermostat would be in the closed position so not flowing well/much.
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VTRDark
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Re: Warming up on the side stand....good or bad?

Post by VTRDark »

Mines out as I was thinking the wrong way as molcules don't get close with heat....doh but maybe the moving around has an effect.
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