re-jetting needed?

[El__burro]

good day,
I have been riding my cb750 k2 for over a month and today I went back to ride my Bmw r80/7 and
i have noticed a huge difference in maximum speed and overall performance.
my cb750 is definitely slower.
i have synced the carbs but not fully understood how to set the air mixture the same for all 4.
also I have replaced the standard air filter for K&H (like) stacks and gone to a 4-2 exhaust system but kept the stock jets..
would i see any difference in changing their size.
if yes, what size?
Thanks
el__burro


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[hairygit]

Yes, increasing the jet size is necessary running stack or pod filters. As they are more free flowing than a stock filter set up the decreased resistance means it pulls less fuel through the jets, and gives a weaker mixture. Every bike will behave differently to given changes, so it's trial and error until it runs as best as it can with the filter/exhaust combination. What size jets are you currently running?

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[El__burro]

The actual jet are 110.
Since i have both pods and 4-2 exhaust system, shall i go 4 up?
Where shall i buy them?
Thanks
el__burro

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[El__burro]

Actually I have just found this..
Shall i go +6 then?
el__burro

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[hairygit]

A U.K. K2 should have 115 as stock, so you're way too small at the moment!

[El__burro]

The bike comes from Italy.
Should I go 4 or 6 up?
Thanks
el__burro

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[hairygit]

Try 4, then you've still got the needles to give you play either side. How has it been riding up to now? Does it feel starved of oomph?

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[El__burro]

It rides fine, I have tried to go very fast but as I said its much less responsive than my other bike. (Bmw r80)
Would reJetting make any difference?
el__burro

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[El__burro]

Not sure what size to look for and where.  Any suggestions?
Thanks
el__burro

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[Bryanj]

Sirius in canada do jet kits or individual jets

[El__burro]

Woaw.. are you sirius.. in Canada?
🤣
What size should I go for?
Thanks
el__burro

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[Bryanj]

Best card parts supplier I have found in 30+ years and no idea on jet size

[totty]

Looks like you're going to have to do this by trial and error, so you probably need to order both +4 and +6. After finding best full throttle performance you'll them more than likely need to adjust needle height, then pilot adjuster and maybe even pilot jet. A lot of work on a four.
I don't know which jets this model uses, but I got my last jets from wemoto and I've also used allensperformance.

[philward]

I've used Allens too - http://www.allensperformance.co.uk/carb-kit/keihin-jet-identification-chart/

[El__burro]

Thanks Phil, I've been looking for jets on both wemoto and allens..
What jets would i need from the link above..?
Thanks a lot
el__burro

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