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Old 06-05-2011, 10:13 AM   #1
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Default It does not start when it is hot

Hello all,
I have a RB T10 RC, it runs very nice in the track and it can finish a 30 minutes race with max 130 Celsius.
The problem is that if I stop the engine and it is hot about 120 celsius then it does not start unless it cools down. I can see the fuel in the silicone tube trying to enter the carburator but it returns and goes back and forth.
I have changed carburator, fuel tank, fuel tubes, air filter, venturi replaced with the normal novarossi and not the tall one from RB.
The engine runs very nice in the track and it idles well for more than 20 seconds. therefore I doubt that it is too lean, a reason that could cause such an issue.
I would appreciate if you could give me some ideas.
Thanks
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Old 06-06-2011, 02:09 AM   #2
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Maybe you are running a little too hot for the engine to be restarted (vapour-lock).
I know engines like the Flash .12 like running around the 120 mark, and Im not sure about the RB Touring engines, but perhaps 130 is a bit too hot.
Unless you cool the carb down before you restart it, then it might keep happening. Do that, or try to get some better air-flow across the carb, that could help.
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Old 06-06-2011, 02:49 AM   #3
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It seems the engine is near end of life, it is the indication when it will not start when it is warm. When you take out the plug and turn it arround you probably do not feel any pinch.

In a race when the motor stalls and will not be fired up again I splash some fuel on the head at the glowplug. It will give a direct cooling which most of the times will work to start the engine again.
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Old 06-06-2011, 10:12 AM   #4
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Hello and thanks for your answers.
I would agree with you in most cases and I would do the same assumptions. However, I have to say that most of the things you describe are not valid in my case. More specifically, the engine is not lean, I have good smoke all down the straight and when I enter the pit lane it idles properly for ever. Therefore, I believe that temperature is not an issue. I have seen other engines starting easily much hotter than that.
The engine is very competitive and still the piston locks on the upper side of the sleeve. The same thing happened since day 1.
That is why I am going crazy.
Thanks again
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Old 06-06-2011, 10:27 AM   #5
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Quote:
Originally Posted by etgdpu View Post
Hello and thanks for your answers.
I would agree with you in most cases and I would do the same assumptions. However, I have to say that most of the things you describe are not valid in my case. More specifically, the engine is not lean, I have good smoke all down the straight and when I enter the pit lane it idles properly for ever. Therefore, I believe that temperature is not an issue. I have seen other engines starting easily much hotter than that.
The engine is very competitive and still the piston locks on the upper side of the sleeve. The same thing happened since day 1.
That is why I am going crazy.
Thanks again
When the engine is hot; Upon restart the fresh itemized fuel charge is actually vaporized before it gets thru the engine due too excessive heat. I would do like the previous post said. I pour a small amount of fuel on the base of the carb just below the air filter neck. This normally cools the carb enough to start a hot engine.

Pass you soon...
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Old 06-06-2011, 04:25 PM   #6
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Quote:
Originally Posted by etgdpu View Post
Hello and thanks for your answers.
I would agree with you in most cases and I would do the same assumptions. However, I have to say that most of the things you describe are not valid in my case. More specifically, the engine is not lean, I have good smoke all down the straight and when I enter the pit lane it idles properly for ever. Therefore, I believe that temperature is not an issue. I have seen other engines starting easily much hotter than that.
The engine is very competitive and still the piston locks on the upper side of the sleeve. The same thing happened since day 1.
That is why I am going crazy.
Thanks again
You could try using an insulated carb. This solves the problem instantly.

When I used to run Max, I had the same problem you are describing. I solved it by going a little bit richer on the bottom side. So the engine had enough fuel to start the engine again.

This is the reason new engines come with the plastic insert at the base of the carb.
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Old 06-06-2011, 08:20 PM   #7
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IMO you're running the bottom end too lean, sure you got smoke, but that doesnt mean the bottom end is not lean. Try to richen the bottom a couple of hours, and then adjust the top for max(or almost max) power.
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Old 06-12-2011, 09:16 PM   #8
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IMO you're running the bottom end too lean, sure you got smoke, but that doesnt mean the bottom end is not lean. Try to richen the bottom a couple of hours, and then adjust the top for max(or almost max) power.
My RB 10 does then same thing. I will give this a try. Thanks
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Old 06-13-2011, 08:27 AM   #9
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it time to replace the sleeve & piston.
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Old 06-14-2011, 12:13 PM   #10
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Originally Posted by Riketsu View Post
You could try using an insulated carb. This solves the problem instantly.

When I used to run Max, I had the same problem you are describing. I solved it by going a little bit richer on the bottom side. So the engine had enough fuel to start the engine again.

This is the reason new engines come with the plastic insert at the base of the carb.
+1,just change with the plastic insert carb,your problem will solve,it nothing with too lean or too rich setting,try nova flash .12 cabruater,u will love it.
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Old 06-15-2011, 01:19 AM   #11
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+1,just change with the plastic insert carb,your problem will solve,it nothing with too lean or too rich setting,try nova flash .12 cabruater,u will love it.
That will help, but with the carb you are using now, probably would be good to richen the bottom end a bit like others have said - would cool the engine a bit but will still give you the power up top via the HSN.
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Old 06-15-2011, 11:11 AM   #12
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130 may be too hot, i run a max mf and its a beast at 100deg/cel. I run 120 max for qual and 100 to 110 for mains and have my engine for three years now, at just 10deg more u putting more wear on the engine.
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Old 06-16-2011, 03:49 PM   #13
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it could be because its too rich on the low end and your not getting eneough sprak from your glow igniter...... or you glow plug is done.. could be so many things
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Old 06-16-2011, 04:10 PM   #14
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Originally Posted by etgdpu View Post
Hello all,
The problem is that if I stop the engine and it is hot about 120 celsius then it does not start unless it cools down.
I doubt it would be because it's too rich, it's just a tuning issue. There are many possibilities:
-0.3mm shim count, maybe putting an extra 0.1mm would solve it (a little cooler, though it would affect bottom vs top performance, or possibly make it better in this situation.)
-Glow plug might be 1 step too hot?

It's very hard to tell here compared to actually seeing it in person.
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