Engine warm up

[rackemblue]

For those of you who do not know the importance of letting the engine warm up for five minutes before takeing off on your bikes for the first time of the day or night. This information I learned in Motorcycle school. The pistons in all bikes are slightly cone shaped smaller at the top than down at the skirt. The reason for this is the top of the piston is going to expand more from the heat on top from all the little explosions of repeated fireing. After they warm up they are steight up and down on the walls from the top to bottom of the piston. The cylinder and head of aluminum also expands and contracts on their respective gaskets. So if you take off before they have expanded your piston is rattleing at the top from being loose in the cylinder and oils and compression can leak from your gaskets. That is what causes the most engine failures or excessive wear and blow by from your head gasket and base gaskets. Harley found this out the hard way when they went from the iron heads and cylinders to the aluminum Evolution motors. We had to change out many cylinder base gaskets and head gaskets under warranty. They were blowing oil every where. They then started changeing gasket material and looking for why until they realized how long it took to warm up and tighten up on the gaskets. Takeing off with a cold motor puts crank case pressue on gaskets and causes them to leak or blow out.

 

[stinkfoot]

I agree. I start my bike with the choke on and when it starts to run I let the choke all the way down and let it warm up for 5 minutes. Next I adjust the idle and check the my exhaust for any funny smoke.

 

[Toothy]

Wow...5 minutes. I'm at 30 seconds to a minute max. Guess I need to sit a little longer?

 

[rackemblue]

The length of time varies if you want to know for sure if it has warmed up enough put your hand on the case below the cylinder and if it hot to you hand it is warmed up enough. I the winter it will take longer than in the summer. Remember this is only when the bike has set overnight and completely cold. Not every time you start it during the day or night.

 

[Russ McClay]

I usually just check the temp by carefully touching one of the cooling fins on the cylinder. Too hot to touch? Ready to go.

 

[Davezilla]

I'll definitely agree on the warm up for the reasons stated above... On my first startup of the day I'll leave mine running in the driveway for at least 5 minutes while I'm doing other things getting ready to go out for a ride, but mine is almost always fully warmed up before I get on the bike and go. Same goes for my Harley but that one won't run right until the engine is warm, especially in the winter or on really cold days I need to go out and start it up and let it idle while I'm getting ready for my ride.

 

[UP Rider]

Start up, finish full cup of coffee and cigarette, go. S'all there is to my start up plan.

Ride safe All

UP Rider

 

[TakeiT]

1 minute is usually enough, however you should let your car, quad anything warm up before using it.

 

[2door]

Five minutes seems excessive to me, especially with an air cooled engine that has no means of cooling itself. No internal cooling fan, no shrouds. To leave one sitting for five minutes without air passing over the cooling fins sounds like it could do more damage than good.

I take my cold engines down my driveway, fire them up and idle down my street with the choke half or less on then open the choke and ride. Less than one minute of engine running time. That goes for summer or winter. Many many miles later, no problems.

What works for some might not be the answer for everyone. Just one man's opinion and experience.

Tom

 

[maniac57]

I've been starting mine by riding off on it for as long as I've owned ht's. Never had any problems with gaskets.
You're overthinking things....
Just ride it!

 

[rackemblue]

i am not over thinking it is not just the gaskets it is excessive wear to the piston and cylinder. you do not have to take my word for it talk to another motorcycle mechanic they will tell you the same thing if they don't he has not been working on them. I worked at motorcycle dealerships for 26 years, so i have torn down engines that were barely broken in with gaulded cylinders from takeing off with cold motors. You can do what you want to I am just trying to help your small motors last a little longer if you want to take off with a cold motor I don't give a hoot.

 

[2door]

You need to keep one thing in mind; these aren't motorcycles. About the only similarity is they have two wheels and an engine. Comparing motorized bicycles and the engines designed for use on them to factory built motorcycles is futile. They are different animals, completely.

Overheating any engine is asking for trouble. Air cooled, means, cooled by air. In the case of our engines that means moving air or air moving over the engine. Not sitting for five minutes idleing.

As in every other aspect of this hobby people need to do what works for them. If it works for you, good. Those of us who have had good luck doing it differently will continue doing what works for us. Both sides of an issue need to be presented here and let the readers make their own decisions.

Tom

 

[rackemblue]

If you think that I am over thinking get you a piston and mic it at the top then mic it at the bottom of the skirt. It will measure smaller at the top than at the bottom. The reason for that is that piston is going to expand more at the top from the heat caused by combustion. so when the motor is cold you are running with a loose piston until the top expands. that is more noticeable in two stroke motors. If you get you a stethoscope and listen to a cold motor at the top end then listen to a motor that has warmed up you can hear the piston slapping on acceleration and deceleration. I was taught by a world record holder at Bonneville. If you check the bonneville speed records you will see the name Woody Leone. He still holds the world speed record for a 650 twin cylinder Triumph 178.26 mph He taught me how to work on bikes some motorcycle dealers will tell he was one of the best mechanical engineers in the world he had motorcycle racers from as for away as Japan bring bikes to him because of his experience with his mechanical knowledg e and his R&D high speed Dyno I learned to work on motorcycles from him and I am not saying I know everything because I learn things every day myself. But if you don't want my input on this site I will shut up and you all can figure it out for yourself

 

[rackemblue]

I Saw at the top of the posting section that if you have something to share feel free to do so. I don't care what you say about the difference between motorcycles and bicycles a motor is a motor and they all require the same things I did not mean for you to set there and burn your dang motor up I happen to know the importance of air moveing over the cooling fins thats what they are there for. I was only suggesting that you properly warm the engine up to keep from blowing head gaskets and excessive piston and cylinder wear.

 

[rackemblue]

By the way I might have not mentioned that working at a motorcycle dealer does not mean I only worked on motorcycles we worked on john deere lawn tractors,Dixon ZTR mowers,chain saws Jet skis,push mowers, Polaris 4 wheelers, and just about anything that had motors, I will be 70 years old in December and retired from A Harley Davidson dealership in 1998 so I have worked on my share of motors. I am only building these bikes to keep myself from getting rusty.

 

[2door]

Sir, I'm not going to sit here and debate this issue with you. I believe I made my position very clear in post #12 above. If you feel that what you are doing is the correct way and it has worked for you then it is the right way, for you. Allow others to do what works for them.

Re: your PM to me, I will not argue that a piston is looser in the cylinder on a cold engine and tighter in a warm engine. That's a product of the coeffecient of expansion of the piston, the rings and the cylinder, and a fact of physics. It is one reason a warm engine runs better than a cold one. I simply don't see what it has to do with the subject of this thread.

Can we agree to disagree and let other members either add to the conversation or let it be?

Tom

 

[rackemblue]

Yes we can agree that you don't like other people to help the readers but you. This site is not for me.

 

[2door]

You need to expect opposing viewpoints. If they don't agree with yours, I'm sorry. It's too bad that you feel as if your advice is so ironclad that it can't be questioned. There are folks here with experience that equals or surpasses yours. It is only natural that you will see opinions that run counter to your beliefs. Expect that and try to be comfortable with it.

I've tried twice to explain to you that if you feel your way is the best way then you should pursue that path and those who agree can do likewise. However there are those who feel differently and it is our prerogative to voice those opinions. That's how a forum works.

Tom

 

[maniac57]

Wow. Sounds to me like this forum may NOT be for you.
We respect other peoples opinions here even if we don't agree.
Don't like a post? Scroll on by.
I was not trying to say you should not have posted your opinion, just what I think of it.
Opinions are like buttholes. Everyone has one, and they all smell bad except for our own.

 

[Davezilla]

All I can say is that if everyone don't do things exactly my way and have every 2 stroke manaul memorized so it can be quoted perfectly then they're WRONG

This is why we have forums... because the above coment is totally freakin absurd... we're here to trade opinions and what works for me may not be what somebody else wants to do or try, manuals are great, but not 100% correct all the time every time. there is a LOT of talent in here and all the help any newb could ask for in order to build a kit and get a bike running very nicely without ever turning a wrench before buying the kit. We don't always agree on everything and we do argue from time to time but we also walk away from our keyboards friends at the end of the day... for the most part... if you ask in here or any forum about break in procedures you'll get a different answer from each member in here, same about oil brands and mix ratios, but if it worked for that preson and that person has had his engine running without issues for any ood length of time it's totally wrong to come out and call them wrong... that's what worked for them.

As far as warmup procedures there are also LOTS of different opinions and those opinions should be respected, especially when it's coming from members who have had their bikes running for years... and still running so whatever they're doing isn't hurting their engine and their opinion should count. I do a lot of things others don't agree with but my engine has never failed me, and others do things I don't always agree with but they haven't blew up their engines either, so we argue about it for a while then shake hands and walk away friends. That's what forums are for anyway...

I fully agree about not letting an air cooled engine sit and run for longer than a few minutes without air flowing over the fins, but at idle with no load the engine won't get nearly as hot as running under load so these time limits are pretty flexable once you consider idle rpm, idle fuel mix, air temperature etc, etc, etc... 10 minutes here in Texas in the afternoon parked in a parking lot outside may be a very bad idea, but 5 minutes in the garage or in the shade on a cool morning would be pretty much harmless.

Unless you know the other person's exact running conditions, be careful before jumping in to correct that person, it may be perfectly ok what they're doing in their individual conditions...

So somewhere in all this long windded post, the point is there's no reason to get all butt hurt when others come in here with a different opinion than yours... at least until you know a little more about their exact conditions...