shayne

G'day from Australia. I have been following your site for some time and find it great. I know there are a lot of members who do track work etc and have a fair bit of knowledge in regards to performance modifications, and I would like a few of you do give me your opinions on a couple of things if you please.

I am rebuilding my 98 model engine at the moment, and have done a few mods to improve things a bit:

Forged pistons 10.1 compression ratio (to run on standard Aussie gas)
Standard cams and valves
Clean up ports only - nothing major
Restictors removed from inlet manifolds
K&N airfilter
Jetting to be done on a dyno
Lightened flywheel
Longer intake trumpets/velocity stacks
Staintune mufflers

As you can see it is fairly mild. My first question is in regards to the exhaust headers. It is common knowledge that these motors love a good set of mufflers, but what about the headers? Does increasing the pipe diameter give any improvement over the standard pipes for a mild motor like mine?

My second question is in regards to the airbox. Taking the lid off appears to be a big no-no. What about making a small increase in the intake of the box? For example ripping out the rubber snorkel we have in the Australian models and increasing the inlet hole slightly, or drilling a coule of small holes in the lid. Has anyone had any success with this for a street bike?

Any advice would be appreciated, and I will be interested in your opinions.

Cheers,
Shayne

Loco

Regarding the airbox: When you install the K&N filter, they give you two block off plastic blocks to put over the auxiliary air intake holes from the base of the airbox. If you find your mixture running too rich even with the K&N, you could always remove those for extra flow. K&N filters allow a TON more airflow than stock filters, I forget the actual figure though (I read the K&N box a few times when I was on the toilet).

I would be wary of drilling holes in the airbox due to the nature of the airflow. While "fire is fire" when it comes to spark, air flow can be tricky and you might be disrupting the flow of air that was anticipated by Honda. ALTHOUGH! I went into a local bike shop and heard the guy behind the counter talking about how he took the cover of his 929 airbox, and the bike has been running like a champ. Seems way too risky to me, I'd hate to have something stupid fly into my expensive K&N (cigarette butt, water, who knows).

From what it sounds like, you aren't going to be adding any more fuel flow just by modding the engine, and the bike should be pretty lean as it is. Changing your main jets will go a long way towards balancing your fuel mixture, and I would try to work it out from the carbs outward, instead of chopping the airbox.

Are you running especially rich or did I miss something? Hope this helps.

Mithrandir

When jetting the bike, make sure you drill the carbie slides. It makes quite a bit of difference to the throttle response. Also, a +4 advance on the ignition made wonders with the snatchiness of the throttle on my old bike. With the airbox, all I did on mine was run the stock filter, but cut off the big transverse piece of plastic that comes on the OEM filter. I didn't think it was worthwhile to take the top of the airbox off. Some bikes this makes a huge difference - eg my former Mille R gained significant torque and throttle response improvements by almost doubling the airbox capacity (remove top and use the bottom of the tank as the new top for the airbox).

shayne

Thanks guys.

In regards to the ignition advancer, I talked to Factory Pro and they recommended with an increase in compression 4 degrees is to much, 2 degrees might be safer, so I have decided to give it a miss for the moment and see how it goes. The increase in compression and lightened flywheel should improve the throttle response. We'll see I guess!

I don't have a jetting problem as such. I am just looking to maximise my tuning when I attempt it on a dyno, and want to get the airflow right before sorting the jetting out. No point jetting it and then increasing the ariflow later. So if can do some mods that we know work that will save on stuffing about.

I was uncertain about drilling the slides. If you have noticed an improvement then I guess it is a worthwhile mod and easy enough to do.

Anyone else have any thoughts on the airbox or the header size?

Thanks,
Shayne

Mithrandir

Ah, the sales guy you were talking to, doesn't know what he's talking about. The stock FactoryPro ignition advancer that they sell for the VTR is +4 degrees. That's what I had fitted to my old VTR, and what I'll be fitting to the two motors I have in my possesion (stock and one I'm building up as a custom).

While you could lighten the flywheel, unless you're after horsepower and not torque, I wouldn't recommend it for the VTR. The motor is lumpy enough as it is, and lightening the flywheel will make it even less smooth. For the moment, I would recommend the ignition advance and carbie work, then see if that is good enough before considering the flywheel.

shayne

Does anyone else have any thoughts on this?

Thanks,
Shayne

jealousyhertz

Can you possibly tell me where I can find a light weight flywheel for my 2000 superhawk? Thanks for your time.

Danny

shayne

Moriwaki will make one I think. One place to get it from in the UK is Revolution racing. www.revolutionuk.co.uk. Roger is the man to talk to I think.

Personally I would whip yours off and get your local machine shop to do it for you, and save a lot of dollars. The magic weight appears to be 2.85kg for a realtively stock or slightly modified engine like mine above.

jealousyhertz

That website doesn't work. Could you verify it for me please? Thanks again.

Danny

mikstr

Hi,

Roger at Revolution Racing is your man for all things VTR (http://www.revolutionuk.co.uk/). He is in the process of machining a lightened flywheel for me that I will be bolting onto my VTR in the Spring. He is extremely knowledgeable and helpful. Just use the link on his site.

Good luck

Micky

CNI Dawg

If you are still having problems getting on his web site here is his contact info:

Address: Smith Green Depot, Stoney Lane, Galgate, Nr. Lancaster, LA2 OPX

Tel: 07970 915 259

Fax: 01524 400182

Email: enquiries@revolutionuk.co.uk