Fireblade 900 RRX - Air/Fuel mixture problem ? - Honda Motorcycles -
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post #1 of 1 Old 09-17-2019, 4:34 AM Thread Starter
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Fireblade 900 RRX - Air/Fuel mixture problem ?

Dears, I'm new on this forum, so I would like to say Hi to everyone.
Few words about me: I'm 38 years old mechanical engineer from Poland, specialized in Air Filtration industry.

From the very beginning of my life I use a Motorbikes/Motorcycles as my primary transportation vehicle, only in the winter time I prefer car.
The clue of this thread is that 3 weeks ago I owned a Fireblade RRX with real 29.000 km (18.000 miles) on the odometer. This Bike is in full stock specification, including paintwork, jets in the carburetors, exhaust pipe and everything else. This is my third SC33.

Before I bought it, it was unused for about 5 years. So I made a standard service > Oil and Oil Filter, Air Filter (OEM from Honda), Coolant, brake fluid, Voltage rectifier (Ducati Energia), Spark Plugs (Denso Iridium IUH27) and carburetor cleaning.

After servicing everything is fine, engine have a full power, run smoothly from 2k rpm to the red line, starts perfectly - cold or hot, no fuel and air leaks. But there is two things that are not normal....

1) When engine is cold (under 65 Celsius degrees), without choke, it's popping quietly to the exhaust but only on rpm lower than 3.500, popping is not regular, with frequency about 1pop/3seconds (Higher temperature = Lower frequency of popping). When the engine temperature is higher than 65 Celsius there is no popping at all. When it's running with choke there is no popping sound.

2) When engine is in normal operating temperature, and when I'm starting to ride, engine is not running smooth onder the 2k rpm's, engine is a little "shaky". I know that this is high rev engine, but believe me, I'm not giving full throttle on low rpm's, I just want to start riding normally without giving 3k rpm on the start. In the past I had two other blades and they were running super smoothly in the same riding style - so I'm sure that this is not correct situation.

In my opinion this two problems are caused by the same source. When I buy this bike Air/Fuel pilot screws were turned as below:
cylinder 1 - 3,5turns
2 - 2,5
3 - 2,5
4 - 2,5
On this settings there was also popping sound.

I thought that somebody made a mistake with this 3,5 turns on 1st bank, so I set all cylinders to 2,5 turns. It doesn't help.

This Honda is standard European model - so following service manual, pilot screws should be 2 turns out, but I'm afraid that with 2 turns it could be only worse.

So I would like to ask you my new friends - Should I go higher, I mean to turn out pilot screws more than 2,5 turns? I'm thinking about 3 turns and check for changes - but it will be quite far away from standard 2 turns...

Popping sound on cold engine, no popping when engine is hot, "shaky" under 2k rpm when riding and normal higher rpm's - it all says that the mixture is too lean, so I'm almost sure to turn out pilot screws more - what do you all think about this?

Thank you in advance for your help.
Toper is offline  
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