4Rt Hotstart

[jrsunt]

sounds like it could be valve clearances. They do get hard to start when hot if the clearances are tight.

[jonnyc21]

I was just wondering about valve clearances... worth a check for sure.

[menglovekai]

www.youtube.com/watch?v=euFH-kP4y1o

Me stating the bike when cold . 11 degreeC in the moring . Just one kick . 
Can you  compare  the Idle speed of my bike compare to other 4rt ? Is it high enough? 


I check and adjust valve clearance as manual . Intake 0.12mm. Exhaust 0.3mm. 

I will adjust it to  Intake 0.15 mm. Exhaust 0.35 mm. 

Is it possible that when you ride long enough that the engine temperature gets higher  until the point where standard valve clearance can not deal with the part's expansion ? 

Or may be i have to check the valve clearance when the engine is hot. 
 

Edited February 5, 2016 by menglovekai

[jonnyc21]

I wil double check my manual but every bike I have ever had was checked cold.

Also you want the valves as in the middle of the range as you can get. I have had a bike where the close side of the range and high heat did make starting a bit hard and when I put it right in the middle it fixed that.

Let us know how it goes.

[cmxi]

www.youtube.com/watch?v=euFH-kP4y1o

Me stating the bike when cold . 11 degreeC in the moring . Just one kick . 

Can you  compare  the Idle speed of my bike compare to other 4rt ? Is it high enough? 

I check and adjust valve clearance as manual . Intake 0.12mm. Exhaust 0.3mm. 

I will adjust it to  Intake 0.15 mm. Exhaust 0.35 mm. 

Is it possible that when you ride long enough that the engine temperature gets higher  until the point where standard valve clearance can not deal with the part's expansion ? 

Or may be i have to check the valve clearance when the engine is hot. 

 

 

Your idle speed is higher than mine -05.

[jonnyc21]

Great news!

[menglovekai]

After 5 day of test . Easier Hotstart  but i still encounter the problem.

so I check the plug, The plug is "dry carbon foul" .  Then i took the air filter out , it looks good  but once i squeezed ,it was full of blue grease .


Oh god . It was just a nasty clog air filter.   

 

 

[menglovekai]

Update on my Hot Start problem . 

If the weather is extremely hot  35+ degreeC  and continuous ride about 30 min. 
There was a lot of vent out the breather hose and The fuel was boiling in the gas tank .

I assume there is a fuel boiling in the injector rail too. So when i start , the Fuel mixture is too lean .(Spark plug never gets wet)
I google a lot and find some word "Hydro lock" .

solution 
1. If the weather is extremely hot and sunny  always park your bike under the shade  , ride for a short period of the time. ( Under cloudy weather with 25 degreeC  there will be no problem at all)
2. If the bike can't start , open the gas cap to confirm there is a boiling inside. park the bike in the shade and wait 10 minutes .  

[guys]

Update on my Hot Start problem . 

If the weather is extremely hot  35+ degreeC  and continuous ride about 30 min. 

There was a lot of vent out the breather hose and The fuel was boiling in the gas tank .

I assume there is a fuel boiling in the injector rail too. So when i start , the Fuel mixture is too lean .(Spark plug never gets wet)

I google a lot and find some word "Hydro lock" .

solution 

1. If the weather is extremely hot and sunny  always park your bike under the shade  , ride for a short period of the time. ( Under cloudy weather with 25 degreeC  there will be no problem at all)

2. If the bike can't start , open the gas cap to confirm there is a boiling inside. park the bike in the shade and wait 10 minutes . 

Or add cooler fuel if possible...

[jimmyl]

The boiling point of a liquid changes with pressure. Lower pressure lower boiling point and vice versa.

As the fuel down stream of the pump is at higher pressure would be surprised if it would boils ???

[richierich]

Hi

I always come acroos "new" 4RT riders at trials struggling to restart hot engines; I have found the most effective way is to find top dead centre (TDC) before attempting to restart from hot. Takes a little practice to find TDC but, from experience, I can confirm that a hot 4RT can be kicked over continuously and will struggle to start but if you locate TDC and give a gentle kick, it starts first and every time.

 

Also, my inlet valves closed up a little recently and made the hot start problem more difficult; I adjusted the inlets to the higher gap in the manual and now is back to normal operation.

 

Setting the idle screw to close to 1900 rpm as possible also helps and be sure to make sure, as someone else said, that there is a little free play in the throttle cable; if the throttle cable is too tight, it will open the throttle valve a little and screws up the throttle body sensor settings making starting very difficult.

[menglovekai]

Eventually, I found the problem .

The Fuel filter was clogged by rust . 

After flush and clean the filter ,  Now the bike can hot start everytime no matter how hot the weather is. 

The root cause may be the crack fuel cap ,So the water can get in when washing the bike  and after parking for almost 2 years.
the rust buildup. 

Thankyou everyone.  

[guys]

I've heard from this rust problem before, but didn't thought of it to link it to hot start problems.

To avoid that problem, I had an aluminium tank bottom on my 2008 4RT (also saves a bit of weight).

I also use Shell V-Power for that reason: less ethanol in the fuel = less water in fuel = less rust and other water related problems in fuel system.

 

Honda finally addressed this problem with a plastic fuel tank bottom.