Hey guys, I have a simple question; with my bikes' setup, do I need a DynoJet (or equivalent) jet kit?

Right now, my 87 bike has a 95 engine, and the p/owner just used the original VG80 carbs when replacing the blown engine.
Right now, it has a restrictive 4-2-1 exhaust system; one of the secondary runners just enters the other secondary runner at a 45 degree angle, then some lump of metal was welded on to hold a 55mm inner diameter muffler.
Even more restrictive (cheap) open air filters are fitted too, each with barely a 50mm inner diameter blocking at least 65% of all the air channels around the beginning of the venturi.
I had it rejetted, the tuner actually removed the stock #120 jets and replaced them with #116 jets... and it stills runs too rich.
It made 80hp to the rear wheel... might just as well ride a Harley (all of the noise and none of the speed).

I now have a stock exhaust manifold on the shelve with both secondary runners merging into a collector box, wich at the end splits up again to the left and right to accommodate the 50mm outer diameter link pipes.
Today I'll go out to find me a nice set of free flowing mufflers, I'll fab up some stainless link pipes from stainless steel myself.
A set of four 55mm K&N cone filters is waiting on the shelve as well.
With the above mentioned setup, do I need a jetkit, or is it possible to tune the engine properly with just jets?
I don't care about having just a few more peak hp, or a power curve that's smoother (both noticeable on the graph but not/barely noticeable on the street).
Wich is what I, in my limited experience with these bikes (and carb in general), would expect to see from a dynojet jetkit?

 

Mate, it's just too hard to call without sticking on the parts, starting it up and seeing how it runs. From the sound of it, it was very restricted by the filters so that should get it breathing in a lot better.

Fire it up and go from there...not much help I know, but it's a bugger to spend $ if you don't need to.

 

Those last few words are the exact reason for this topic

Btw, is there a performance gain to be had from installing the carbs that belong to this engine?

 

I realise that's your point mate, but the only way you'll know is to try it.

As to the carbs, if you're only getting 80bhp at the rear wheel then I'd say that you should put the right ones on there.

These bikes have bulk power dead standard so I'd say Honda knew what carbs to fit

 

True, but the bike made lots more power without any form of filters, even with the hugely restrictive exhaust.
The guy showed me dyno graphs from several other CBR1000F's he had done before, and they were all making about 120hp to the rear wheel; he told me the filters were to blaim and the exhaust didn't help much either.
I think I'll just try to have it rejetted, if I need to get a kit, eBay is my friend I suppose (the shop charges 200 euros for a DJ jetkit, excluding fitting and rejetting the carbs... wich is nearly 300 US dollar and I've seen these kits floating around at about 115 bucks?).

Thanks for your replies Dave

 

You're welcome. Sorry I can't give a straight yes or no answer.

I've got a full V&H 4 into 1 and a K&N drop in filter. I had to fit a jet kit, as I couldn't get it to run right, and put a Dynojet stage 1 on. I dicked around several times with needle heights and jet combinations before getting it to run just right...had the carbs off about 6 times.

However, when I cracked the throttle wide pretty fast there was a massive lag and no power for a split second. In the end I ditched the springs that came with the kit, as they were just too light, and went back to the originals. A bit of a waste of $ really!

Now it runs great. Never put it on a Dyno...I'd freak and punch somebody for revving the **** out of my bike, but it hammers.

 

Hey:

The 87-88 carbs work fine on the newer motors, jetted down abit 114-118 mains, +1 up on needle. I would not waste my money on a jet kit, as they mostly have larger jets and springs that may not help, that is not what you may need in ths combo. 89-91 have larger carbs if you are just looking for peak power only. Also 39mm Keihin FCRs for a 94-95 CB1000 also work if you use pod filters and not the std airbox as they need a longer intake tube/hose made for them to get the best street manners from them but are the absolute best for power, but costly.

But I like the 93+ non emmissions flat side type that came on the motors as they were already rich so adding a good pipe and large pod filters and you were already set up. you can find them on Ebay for $150.00 USD. They also have great street manners. Just make sure they are not California or a restricted Emmission model carb with the extra hoses and such.
The exhaust that flow good are Akrapovic, V&H, and Micron if you want to keep the centerstand. The OMT or Yoshimura race work good if that does not matter. Plus you have Motad, Arrow, Blue Flame, Nexxus, and Black Window out there in your market plus many others that all work very well.

(Also if your motor has back pipe and not detachable side water outlets your engine is a 94-95 CB1000F engine they have way less power -20/30 BHP, diff cams and only 5 speed gearbox, but are the same externally. Good Luck with you choice.) Just got a look at your link on my computer and not the phone and see the motor is a CBR one, not CB, some markets had 100 BHP restrictors put in the Carb intake boots and Exhaust plus retarded timing, to keep it below the norm for other markets (and can be removed). Where or do you know where the motor came from originally? They just choked it down to 100 BHP that way.


Dub

 

@ Dave
I'll just have it tuned on a dyno, that'll make for the best possible result.
And it's nice to know how much power I've got too

@ Dub
Exhaust will be a stock manifold (for now), custom made link pipes, and two Laser oval carbon straight through cans.
I don't have a center stand anymore, just the side stand.
You say +1 on the needle, but they're not adjustable... isn't that why I would see benefit from a jetkit?
Restricted emission models are very uncommon over here; my bike is for the European market, not US, and when the boots would have had restrictions in them I'm sure the guy who rejetted it would have mentioned that.
I think I'll just stick to these carbs for now, and see how much power it makes... if the dyno graph looks like ****, I'll just go out and search for a set of better carbs
The engine has a six speed and no coolant hose on the carb side, so rules out having a CB engine in stead of a CBR (luckily).

 

If it were me I'd just get it back to original spec. I don't use all the power I have now.

Though I still have a louder exhaust and want pod filters for other reasons, but I wouldn't spend any money trying to drag more power out of them

(I'm at work now and my MX bar and risers just arrived. WOOHOO!! 'fighter time, bitches!!)

I just love modding bikes...

Tim.

 

One thing for sure, put the factory head pipe and collector back on. It will give you more low end and smooth her out. As with my TB single can, have a shop turn an aluminum plug to fit the left side port of the collector and just use the right side. Get a bigger can for that side. Less $$$ and weight than two cans.