Will not start when cold

[nfriday]

First off, hi everyone. Name is Neil, I'm from chilly michigan, and I am a proud owner of a 1981 xs400H special 2. Now down to the nitty gritty. My bike is wonderful in the warm weather, not so much in the cold. I guess I should be more clear, once started, it could be 10 degrees out and it wouldn't matter. It WILL NOT start in the cold. Not with ether (I know it's bad) and full choke, nothing! To start with the basics, fuel is there. New petcock, fuel filter, and line. Air filters are clean, carbs are clean. Very good on compression test. But all of this shouldn't be off, because it runs wonderful! Personally I am wondering if it could be valve clearance, thoughts? And as a side note, left a space heater on the engine for a while, and wouldn't you know it started right up! I'm about to lose my mind...lol

 

[Scorpio1963]

Mike bike is very cold natured also.I have to use starting fluid on realy cold days to get it to fireup.Also put a heater next to the crankcase and get the oil so it flow better.Maybe your plugs are weak.Welcome from another Michigan member

 

[XSLeo]

On your carbs there is what most people incorrectly call a choke. It's not a choke, a choke cuts off the air in the carbs. What it is is an enrichener, it adds extra fuel.
When you open the enrichener a circuit in the carb adds extra fuel. This fuel flows from the float bowl through a starter jet. This jet is pressed into the float bowl. If the jet is plugged your enrichener can't add extra fuel.
This makes cold starts very hard.
Remove the float bowls and be sure this jet is clear.
I wish I had pics to show this but I don't.
On the float bowl there is a hole down in one side. This hole has a brass tube going into it from the carb body. At the almost the bottom of this hole is the jet. Just below the jet is another hole that goes sideways out into the float bowl. It often clogs at the corner were the hole from the top and the hole sideways come together.
If you look down into the hole while shine a light into the float bowl you should see the light shining in the hole. If not it's plugged.
Use the tube on your can of spray carb cleaner to shoot cleaner in that hole till it sprays out into the float bowl. If you can't get the plug that way use the twist tie off a loaf of bread. Strip the cover off about 1/2 inch of one end. This leaves a thin sift wire. Use this wire carefully to probe the holes and jet. Use more carb cleaner Repeat as needed to clear the plug.
Reassemble and your bike may start better when cold.
Another thing is that when the bike get very cold the oil gets stiff. This makes the engine harder to turnover. If using the e-start it draws much more current to turn the engine over. This can draw the battery voltage down far enough so the ignition can't fire the plugs.
I have a spare battery, it came out of my van when I put the truck battery in it. Anyway I use this battery as a jump start battery. To use I set it next to the bike. Hook a set of jumper cables to the battery, negative to a frame ground, a foot peg nut works well. The positive a put a long bolt, a 1/4 or 5/16 by 3 or 4 inches long.
Now I turn bike on. In stead of using the start button touch this bolt in the jumper cables straight to the starter. Where the cable hooks to It Or at the other end of the cable where it hooks to the starter relay. Which ever is easier. This sends the jumper battery power straight to the starter. This leaves the bike battery to just run the ignition. This gives the ignition full battery voltage.
This should get the bike to start on those cold mornings.
Leo

 

[Scorpio1963]

If you rejet to a bigger main size it should make it easier to start also on those cold days.

 

[XSLeo]

Not really, The main jet only effects the 3/4 to wide open throttle. The enrichener and pilots effect the starting and idle. The needle and needle jet effect the 1/4 to 3/4 throttle range.
This is why when carb tuning you get the mians right first. Then adjust the needle for the mid range and then the pilots and mix screws for idle.
Leo

 

[nfriday]

Thank you guys for the wonderful input! So as an update, put a heater on the crankcase for an hour, sprayed some ether, and wouldn't you know first kick it started right up. I am personally leaning towards blaming my troubles on the oil. Does that seem logical? Also I'm running 10-40 since in michigan. Also sound about right?

 

[Scorpio1963]

10-40 is the right weight untill its warms up around here.I dont think they make 5 or 10w/30 motorcyle oil.Like I had previously mentioned my bike is the exact same way.Wont start unless the oil is warmed and battery is 100% charged.After its warmed up it will start everytime well it did before I rejetted everything.If your bike isnt stored in a warm place after riding disconnect it and keep it someplace warm.I used to have battery warming plate that i used before it broke.

 

[nfriday]

Looks like I might have to start doing that. Also, weird question....what do you think of a magnetic truck engine heater for the crankcase?

 

[Scorpio1963]

It wouldnt be a bad idea ta all only thing is I think our crankcases are made out of aluminum so a magnet wont stick LOL,I even thought of suggesting get an oil dipstick heater for it.Those are pretty cheap.

 

[nfriday]

I will for sure have to look into that. Thanks for all the great help guys!

 

[Buccaneer]

Hey nFriday - did you resolve this problem? What was the answer? I have a similar problem, see new thread.

 

[Bizzy13]

W/ these old bikes not starting cold bit easy in warmth, it's always that big heavy 20/w50. My old KZ would kill a battery in cold weather but in warm it'd fire right off. Thick oil gets real thick when it's cold.
And it is possible people call the choke a choke because on the pull button it says "choke".
And yea, main jets will not help this situation.

 

[kebabs]

On your carbs there is what most people incorrectly call a choke. It's not a choke, a choke cuts off the air in the carbs. What it is is an enrichener, it adds extra fuel.
When you open the enrichener a circuit in the carb adds extra fuel. This fuel flows from the float bowl through a starter jet. This jet is pressed into the float bowl. If the jet is plugged your enrichener can't add extra fuel.
This makes cold starts very hard.
Remove the float bowls and be sure this jet is clear.
I wish I had pics to show this but I don't.
On the float bowl there is a hole down in one side. This hole has a brass tube going into it from the carb body. At the almost the bottom of this hole is the jet. Just below the jet is another hole that goes sideways out into the float bowl. It often clogs at the corner were the hole from the top and the hole sideways come together.
If you look down into the hole while shine a light into the float bowl you should see the light shining in the hole. If not it's plugged.
Use the tube on your can of spray carb cleaner to shoot cleaner in that hole till it sprays out into the float bowl. If you can't get the plug that way use the twist tie off a loaf of bread. Strip the cover off about 1/2 inch of one end. This leaves a thin sift wire. Use this wire carefully to probe the holes and jet. Use more carb cleaner Repeat as needed to clear the plug.
Reassemble and your bike may start better when cold.
Another thing is that when the bike get very cold the oil gets stiff. This makes the engine harder to turnover. If using the e-start it draws much more current to turn the engine over. This can draw the battery voltage down far enough so the ignition can't fire the plugs.
I have a spare battery, it came out of my van when I put the truck battery in it. Anyway I use this battery as a jump start battery. To use I set it next to the bike. Hook a set of jumper cables to the battery, negative to a frame ground, a foot peg nut works well. The positive a put a long bolt, a 1/4 or 5/16 by 3 or 4 inches long.
Now I turn bike on. In stead of using the start button touch this bolt in the jumper cables straight to the starter. Where the cable hooks to It Or at the other end of the cable where it hooks to the starter relay. Which ever is easier. This sends the jumper battery power straight to the starter. This leaves the bike battery to just run the ignition. This gives the ignition full battery voltage.
This should get the bike to start on those cold mornings.
Leo

I know this is an old thread. I'm having the cold start problems .Leo ill give your advice a go and glad I found this thread. what I've been doing is taking the plugs out and heating them up .it starts first time.its just annoying having to take the plugs out .

 

[CaptChrome]

I will add one thing here that may be controversial. When I start my bike for the first time in cold weather (what I define as ambient temperature where the bike is sitting below 50degF / 10degC), I always kick start it. The electric start on this bike is not all that strong and battery performance degrades with cold temps. I perfer to have all of the available battery capacity go towards providing a strong spark. So, kicking the bike helps with that.

I put the enricher all of the way out, and with fuel on (go to prime position on the petcock if you need to) give the bike at least three full kicks to draw fuel through the carbs and into the cylinders. Then I turn the main switch on and one or two kicks usually gets the bike running. After the bike is warm from riding, I use the electric start if I need to.

 

[kebabs]

I will add one thing here that may be controversial. When I start my bike for the first time in cold weather (what I define as ambient temperature where the bike is sitting below 50degF / 10degC), I always kick start it. The electric start on this bike is not all that strong and battery performance degrades with cold temps. I perfer to have all of the available battery capacity go towards providing a strong spark. So, kicking the bike helps with that.

I put the enricher all of the way out, and with fuel on (go to prime position on the petcock if you need to) give the bike at least three full kicks to draw fuel through the carbs and into the cylinders. Then I turn the main switch on and one or two kicks usually gets the bike running. After the bike is warm from riding, I use the electric start if I need to.

I'm dragging some good info out you now.lol I'll give this a bash .I once had a honda hornet 600 with manual choke .there was a special sequence to start it .if it didn't start. u had to let it sit for 15 minutes and start the sequence again.oh well looks as though carbs are coming off again.ive lost count now.ill need to order 2 replacement gaskets as the ones that are on are starting to tire with me pulling the carbs apart so often.

 

[kebabs]

I'm dragging some good info out you now.lol I'll give this a bash .I once had a honda hornet 600 with manual choke .there was a special sequence to start it .if it didn't start. u had to let it sit for 15 minutes and start the sequence again.oh well looks as though carbs are coming off again.ive lost count now.ill need to order 2 replacement gaskets as the ones that are on are starting to tire with me pulling the carbs apart so often.

want to thank you so much for all your help on this bike.id like to get u a gift for doing so.whats your address ?

 

[kebabs]

i have the idle set at 1250 when really hot ,the throttle stop screw is barely touching the butterfly bracket .do you think i should turn the revs up .maybe thats why its not starting when cold?want to thank you so much for all your help on this bike.id like to get u a gift for doing so.whats your address.?

 

[gpounce32768]

With the enrichener on it is helpful to have the butterflies mostly closed, so the vacuum will get fuel thru the enrichener circuit. Opening the throttle bypasses the vacuum. On my '82, there is a brass tube which extends down from each carb into a well in the side of both bowls, which has a port open to the well bottom. Thats where the enrichener draws fuel- its important that port is open so fuel can get into the well for the brass tube to pick up, and its important for the gasket to seal around the well also.

Those ports were clogged on my bike's carbs which made it nearly impossible to start cold. Problem solved after I cleaned out the ports. The clogs were quite hard and looked just like the aluminum around the ports, I had to clear them out with a small drill bit.

 

[kebabs]

With the enrichener on it is helpful to have the butterflies mostly closed, so the vacuum will get fuel thru the enrichener circuit. Opening the throttle bypasses the vacuum. On my '82, there is a brass tube which extends down from each carb into a well in the side of both bowls, which has a port open to the well bottom. Thats where the enrichener draws fuel- its important that port is open so fuel can get into the well for the brass tube to pick up, and its important for the gasket to seal around the well also.

Those ports were clogged on my bike's carbs which made it nearly impossible to start cold. Problem solved after I cleaned out the ports. The clogs were quite hard and looked just like the aluminum around the ports, I had to clear them out with a small drill bit.

thanks for the info.ive noticed the enricher rod where it goes through the first carb the rubber grommet it passes through has a very small leak.also when I pull the enricher out its not staying out .I have to hold it in place. is there adjustment for it?

 

[CaptChrome]

when I pull the enricher out its not staying out .I have to hold it in place. is there adjustment for it?

The enricher operating rod has detent holes drilled into it and there is a small steel ball backed with a spring in a recess in each carb that locate in the operating rod detents to hold enricher in the off/half/full positions. The small balls and springs are probably missing as if you don't know they are there when stripping the carb down they are easily lost. If you need some, the balls and springs are still available from Yamaha:

ball - P/N 93501-08001-00
spring - P/N 583-14589-00-00

One of each is needed for each carb.