All clean and running great but bogging 5k -7k?!

[pynchy]

Hi everyone,

I have a 92 super four.
I recently changed the oil, cleaned the carbs spotlessly and set them up asper here http://www.factorypro.com/tech_tuning_p ... gines.html, new Denso sparks, new airfilter.

Before I did any of this it bogged very badly from 5k -7k no matter the gear.
Since the changes the bike runs utterly amazing in every range apart from the 5k -7k area. It really starts to notch up the torque from 4k - 5k and then hits a wall, this is really a nice range for commuting and i'd like it to work :). I dont think it is the needle height or to do with the main jets as I have tried various setups which do not affect this range at all.

Two things I have heard it could be
1- the Helmholtz effect... the airbox is not working properly with the carbs caused by piston frequency vs helmholtz of airbox. ( i dont think it is this)
2 - The clocks... could the resistor on the CDI trick sort this out.

Any help from people who also have had this problem would be appreciated.

[CB 4]

HI yer i recently picked up a super 4 for the wife but think she is out of luck, brill bike to own and ride comfy nippy and has got some charter,not sure if this may help have found that these bikes like to be set up perfectly or the get very grumpy, would may be take alook at your generator output should be 13voltish mind ran bad at 5 to 7 k then developed a misfire and the batt went was a duff regulator and ad to put a new batt on.If the carbs are ok then may be wortha look if not a dyno run would be worth a look about £30 quid would look at fueling etc.and help with diagnostics etc.reg c

[pynchy]

Thanks CB4,

I had a new rectifier put in a few months back and nearly sure the battery is relatively new.

May well consider the dyno run alright.

[CB 4]

Goodevening , mite be still worth checkin output of genny with ameter recently fixed a bike with new bits, did turn out to be another knackerd regulator think was a cheaper unit fitted one with cooling fins been fine the sealed one was not very good the owner fitted previous, yep think a dyno would help did my trident took some advice and did the work myself took a while but now goes like hell after a full set up and some work . cheers c

[pynchy]

Thansk CB4,
I checked the battery and charge going to it and its reading in the high 12 sometimes 13volts

so the update is:

I put some STP fuel system clean in the tank, this made every rev range more powerful and partially stopped the bogging in the 5k-7k... but its no where near gone.

So im thinking ill try and shim the needle up again to see does that sort it out as it seems to be a fuel related problem. If this makes any difference im going to get it dynoed immedately.

Ill post back here after.

[CB 4]

hi put my trident onto k and n power filters tuck 6 months of buggerin about 2 sets of pissed off neighbours revin the bugger to work on it and about £100 quid in dyno fees used there advice to fix me self but it def helped , works and goes pefect now carbs on modern bikes are a bit of a bugger to set up so dyno will help and can help in other areas to many thx c

[nictecninja]

hi put my trident onto k and n power filters tuck 6 months of buggerin about 2 sets of pissed off neighbours revin the bugger to work on it and about £100 quid in dyno fees used there advice to fix me self but it def helped , works and goes pefect now carbs on modern bikes are a bit of a bugger to set up so dyno will help and can help in other areas to many thx c

Hi,
whatever you do do not use K&N / S&B seperate filters on a bike with CV carbs as they DO NOT WORK WELL!
cv carbs need still & constant airflow that is why race bikes with open carbs / single filters run flat slide carbs.
Hope this helps a bit Paul.

[CB 4]

hI Paul, set up was a total nite mare but did get there in the end with glitch free carbs , dyno showed 105 horses slightly up on stock with better mpg to be honest there is nothin wrong the the stock air box but a new seat unit ment the box ad t go.U can get filters to work but the man hours and power gains r not worth it stock air boxs 1990,s bikes is normaly v good.cheers c