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Discussion Starter #1
My RD07A is experiencing hesitation/surging from about 60 through to 70 mph when holding a steady throttle or when rolling back on the gas from a steady throttle in this speed band. You can accelerate through these speeds and it improves somewhat but never really goes away in this speed band. The bike performs smoothly outside this speed band. I cannot decide whether it may be a fueling issue or an ignition issue. I changed the jetting from 118.5 front and back but this did not resolve the problem.

As I have collected many spares in my time of @ ownership what is my first port of call for replacement from your collective knowledge?

I have a FACET fuel pump fitted, 120 front jet and 122.5 rear jet, iridium plugs, original coils and R1 rectifier, chokes blanked off, pipercross air filter and leovince aftermarket can.

Many thanks,

Ian.
 

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Shouldn´t you have 120 on the rear as well? Isn´t it only the older rd04:s that have bigger on the rear?!

I think you have a problem with your fuel not ignition.
 

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Discussion Starter #3
Hi IsoIivari,

Thanks for the response I had previously 118.5 jets fitted front and rear but problem remained. I didnt want to go right back to the original 115 jets with the aftermarket can in case it runs too lean. I may change the relevant ignition parts first and if they do not resolve the issue then I will take the bike to a Dyno tuner to investigate the fuelling.

Ian.
 

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Check where airbox clamps to the carbs. If done up too tight they ride up and you get a symptom similar to your description. I used to leave mine loose and the airbox almost just sat on the carb mouths.
 

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Hi IsoIivari,

Thanks for the response I had previously 118.5 jets fitted front and rear but problem remained. I didnt want to go right back to the original 115 jets with the aftermarket can in case it runs too lean. I may change the relevant ignition parts first and if they do not resolve the issue then I will take the bike to a Dyno tuner to investigate the fuelling.

Ian.

The jet differens wont make that problem but something happends at that speed?
YEN_POWELL might b right. :thumbup:
 

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Discussion Starter #7
Hi Guys,

I specifically checked the diaphrams when rebuilding the carbs for any damage and reseated the airbox to carb connection many times to get just the right tension in the clamps as per Yen's recommended procedure for lightly pushed onto the carb mouths.

Ian.
 

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Mine did that when running lean on standard jets but I have 120's in both carbs now, there's no way yours should be running lean.

Might be worth unplugging the throttle position sensor?
 

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Sounds like its running lean have you got a aftermarket filter or and can ? air leak ? does it pop and bang through the exhaust when letting off ?
 

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Discussion Starter #11
Hi Packman,

The bike does have an aftermarket exhaust and pipercross air filter fitted but does not pop or bang through the exhaust on deceleration. I cant really tell if I have an air leak. I have replaced the fuel filter between tank and pump but this made no difference.

Ian.
 

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Did it feel like this when the weather was warmer as this does affect the mixture quite a bit , Warmer the weather the mixture richens up colder it leans the mixture out ......
 

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Check for air leaks buy getting eaither brake cleaner or carb cleaner and spray it around the carb/air box area , esp with brake cleaner keep it away from the spark plugs , if there is a air leak the revs will rise pretty quick :thumbup:
 

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Discussion Starter #16
I am taking the bike to bits over the weekend checking and testing parts, if no faults or issues found replacing all the fuel and ignition parts I already have one at a time starting with the fuel pump then reg/rect as they are easiest to replace. Then moving onto spark plugs, coils, carbs fitted with 120 jets front and rear.

I will check for air leaks in the fuel system before replacing any parts using the spray method with wd40 which I understand will do the same and may be less aggresive.

Thanks to all for the information and guidance and I will advise the outcome which I hope will be positive.

Ian.
 

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No problem also make sure both the big and small breather pipes from the bottom of the tank are not kinked this will cause a air lock in the tank and fuel will not flow well resulting in lack of fuel in the pump and hesitation , and ok on the WD40 yes brake cleaner is rather semtex like lol , sounds more mech rather than electrical also check the tappets while the tank is off.

:thumbup:
 

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Discussion Starter #18
Hi All,

Apologies for the delayed update but I have been spending a great deal of time trying to hunt down the problem and as yet to no avail.

So since my last post I have swopped the regulator/rectifier, fuel pump, spark plugs, front coil, one front coil lead that was not metering out consistantly, put in OEM keihin 120 jets front and rear and cleaned carbs again. Bike is still surging between 60 to 70.

Next I plan to swap CDI cause its easy, check valve clearances, check timing, swap rear coil, swap carbs and if all this fails go back to standard 115 jet front and rear with original exhaust and standard air filter.

Ian.
 

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Discussion Starter #19
Ok finally got the problem fixed but unfortunately a bit of a cop out as I went back to standard setup. So 115 genuine jets front and rear, original honda exhaust and standard pattern air filter. Now bike runs smoothly in all gears and throttle openings with no hesitation or surging. So it looks like that if I want to use the leo vince can and pipercross air filter then a full dyno session will be required but as this has pissed me off so much I will stick with standard setup which my neighbours will be no doubt thankfull.

Thanks to all for their help and suggestions on my problems.

Regards,

Ian.
 
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