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Anyone Ever Rebored/overbored A 5/6Th Gen


Mohawk

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Did it fit in the frame with no issues ? Rumour has it that the 5th gen cam covers wouldn't fit part of the frame.

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Hi Phil, be careful with the rapid bike ignition advance on the 5th gen engine.

I just did some test runs today on standard pump gas (95RON) to see how the ignition advance would work.

My initial setup was PC3 map extrapolated into RB Racing fuel map, with V-tec ignition map reduced by 1 degree for all cells, but with a max value of 2.5degrees. To explain that if cell said 1-3 it was reduced by 1. If cell said 3.5-5 then it was set at 2.5.

This seems to work across the whole rev range, but need some more miles to confirm.

So today I changed the max advance to 3 degrees which was fine up to an indicated 5500rpm, but under load it would pre ignite causing bad stumbling, so reset back to max 2.5 including cells that were originally 3, same result would not even rev correctly on the stand :(

So now back to my initial ignition setup. Have a day booked off on Wednesday, hopefully weather will be fine & I can get some miles o the bike to see how the fuelling adjusts.

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Hi Mohawk

I'll take a look at the advance as I normally run 95 RON over here in NZ.

As far as the cam covers not fitting, I've got no idea who thought that.

They fit fine.

The issue is getting the 6th Gen coil packs to fit.

As can be see from the photos, it's sitting happily in the frame and I've got plenty of working space around the covers.

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Well the beast lives.

Fired it up today and whoohoo

Had a bit of a scare to start with as it wouldn't start.

Plenty of spark but the plugs were bone dry. No fuel.

I was trying out the new to me throttle bodies/injectors that I'd ported and matched.

So went back to the stock units of my 6th Gen engine and away she went.

Took it for a 10k ride just to make sure all was as it should be and I was amazed at the smoothness of the transmission.

It feel like it will pull well once I've run it in.

Definitely less down low compared to the 6th Gen but it feels that it wants to run.

I'll post the final images and a short video later.

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Awesome!

As far as not initially starting with the new injectors and throttle bodies, my bike took forever to start with my new injectors/throttle bodies/fuel filter too. Really scary stuff, but it makes sense because the whole fuel system was bone dry.

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You need to prime the Fi best done by bleeding at the pressure regulator as a dry system will not make pressure to to activate the pressurebypass so you are waiting for the injectors to bleed the system & they are not open long enough.

Good to hear it running, can't wait till you have it run in & give it some beans ;)

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Thanks guys

Didn't think about bleeding the fuel system.

With the new bearings and cams I didn't want to crank it too long without it firing up.

Now that I've had it running for some time, I might give them another go.

Cheers

I need to run it in before it goes anywhere near a dyno.

Then we will see what occurs.

Honestly, I'm not interested in paying to find the difference between stock and modified.

I really am only concerned with what I've got now.

Phil

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Yeah I sometimes think this whole exercise would be easier on a Vtec engine. Adding extra head space a doddle. You could always remove some more material from the inter valve ridges to reduce CR if you think it's too much.

I did some thinking & if you lose the anti-lash gears, then you could separate two gear wheels & make an adjustable cam for degreeing, but like everything else on a V motor twice the count & twice the cost in both time & money.

That'd be one of the first things I'd do if I had a fifth gen. Remove those anti lash gears. Free power :)

Hey Mohawk, got a question for you.

The cams came back fully disassembled and as I didn't pull them apart before sending them off I'm unsure as to re-assembly of the spring/pins and what holes they go in.

Do you remember from yours? Here is a couple of shots.

attachicon.gif20140917_202530.jpg

attachicon.gif20140917_202709-1.jpg

Any assistance would be greatly appreciated.

Cheers

Phil

Just to clear up a discussion had over the weekend, these are the "cam silencing gears", right? The slightly offset gears on the end of each cam, and nothing to do with the gear stack running up from the crank to the cams?

I looked up the mod on the RC51 side of things, and couldn't come up with any pics or how-to, but that's the impression I got. Much debate (8-10 years ago) over the effectiveness and possible detrimental effects. But, if I read it right, each gear and associated spring and hardware is 15 oz. So nearly 4 lb. of rotating mass lost. Also debates on the amount of noise generated.

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Yep, they are the anti-backlash gears as you say.

There is a lot of conflicting discussion on whether to run them or not but without them my motor had about a 1/2 deg of movement on the cams and that stacks up to 1 deg at the crank.

So mine got fitted.

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Thanks guys

Didn't think about bleeding the fuel system.

With the new bearings and cams I didn't want to crank it too long without it firing up.

Now that I've had it running for some time, I might give them another go.

Cheers

I need to run it in before it goes anywhere near a dyno.

Then we will see what occurs.

Honestly, I'm not interested in paying to find the difference between stock and modified.

I really am only concerned with what I've got now.

Phil

+1

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On this forum in the last 6 months or year, there has been some efffing brilliant work going on that has actually been completed- big bore, good front end conversions, some fighters, big airbox, racing module, big TB/injectors....

I've gotten sidetracked with my fighter, but it has been amazing to read a few of these builds.

Nice work.

Just need to combine all these mods into one great big F off motor...

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Yep one F off big motor would be good but I'll settle for my "little" 825 and see how that goes just at present.

You're right, there has been some really good work over the last 12 months. And so may it continue.

That is what is so great about a forum like this where there are plenty of people willing to "have a go"

Cheers

Phil

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On this forum in the last 6 months or year, there has been some efffing brilliant work going on that has actually been completed- big bore, good front end conversions, some fighters, big airbox, racing module, big TB/injectors....

I've gotten sidetracked with my fighter, but it has been amazing to read a few of these builds.

Nice work.

Just need to combine all these mods into one great big F off motor...

Maybe, just maybe... :cool:

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Synced the starter valves flat and determined that one of my injectors was not playing the game correctly, so swapped it out for one of my spares.

All good now and off idle it is nice and smooth.

Then I took the new motor for about a 100 k run today limiting it to 7000 rpm and I'd have to say it's got real potential.

Even to that rev limit it pulls like a 14 year old school boy!

Going to try and get 4 to 500 k on it this weekend and start to see what its like further up top.

The My Tuning Bike is doing a good job building my map from a zeroed base.

From the overall feel of the motor it is soooo smooth, so the lightening and balancing I did seems to have been for the better and I must have kept the balance factor nice and close.

I'll keep you posted.

Cheers

Phil

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