Big Bore and Gas Flowed Head Project - .: XT660.com

richardsracingmad · # 1 23-08-10, 12:40

Ok, after my Stage 3 DNA Airbox mod (with a Power Commander and cans), I am looking at doing further modifications now to compliment the DNA Airbox.

What is so good about the DNA Airbox, you don't lose any power or torque anywhere, and the improvements are in a very wide area of revs, right from just above tickover to the rev limiter. This makes it a cracking mod in my books.

(With some mods, you lose power at one end, and gain on the other end; normally the top end of revs).

So, I am looking at a Big Bore, which should give me gains through the rev range, and a Gas Flowed Head.

This should give me a nice and smooth power boost, and I am hoping for a total gain, with my existing mods, of around 10-12hp over a Standard bike.

I have just started this project, it will probably grow and change a bit, and have sourced a second hand barrel, but I am looking for a spare cylinder head. If anyone has one, please pm me, thanks.

Kev · # 2 23-08-10, 13:11

You will need these.

http://cgi.ebay.co.uk/GENUINE-YAMAHA-CYLINDER-BASE-GASKET-XT660X-XT660R-/380239567677?pt=UK_Motorcycle_Parts

http://cgi.ebay.com/ebaymotors/Yamaha-Raptor-Grizzly-700-EST-Top-End-Gasket-Set-103mm-_W0QQcmdZViewItemQQitemZ220636955493QQptZMotorsQ5f ATVQ5fPartsQ5fAccessories

http://cgi.ebay.com/ebaymotors/COMETIC-EST-TOP-END-KIT-103MM-YAMAHA-RAPTOR-700R-06-_W0QQcmdZViewItemQQitemZ380260180414QQptZMotorcycl esQ5fPartsQ5fAccessories

I would use this piston if I did it again. The difference between a 102mm 11.5:1 & a 103mm 11:1 piston would be less than 1 HP difference.

http://www.tqsatv.com/proddetail.php?prod=RAPTOR-700-TECH-PISTON

richardsracingmad · # 3 23-08-10, 13:48

Kev...thank you for those links!! Top Geezer!! I was wondering.........

Firstly....I didn't realise the bore needed plating, however I have found someone who does Nikasil ...so no problem with that. Would the bore wear out quickly without it? Is it an alloy bore, coated as standard?

Secondly,

...on the Carillo site , the CR pistons are either 11:1, 12:1 or 12.5:1?? Not 11.5:1 ?????
Is the CR piston forged, and the others not? Is that why its dearer/better?

I have found a JE 103mm piston kit 11:1 (item no. 360083541989 on ebay.com) , he will send it carriage free to the UK at $171.99, and a top end gasket set for $68, about �155........I'm think I'm going to go for that..........

Thirdly, do you think a gain of 10-12 hp is on with this, over Standard, with my mods?

A7 UFO · # 4 23-08-10, 13:49

being just up the road from you, I'd be interested to see the results of your conversion

Kev · # 5 23-08-10, 23:20

You will need head work & a +2mm throttle body to get that HP with a standard cam.

All the research has been done on these conversion have a read on what HP you get from what mod in the mod section.

Have a look at my dyno runs with just the big bore with a 11:1 102mm piston it got an extra 2.5 HP gain so I would expect the 103mm to have around 3 to 3.5HP gain. You would have less vibration from the motor with a 102mm piston unless you get the motor balanced.

CP do make a 11.5:1 is has been around for a while now, I have seen good results with this piston with dyno runs. The link I gave you is a valid.

richardsracingmad · # 6 24-08-10, 08:50

Thank you Schoemrich for the barrel ! I collected it last night....you have a nice bike project XT there mate, I am looking forward to seeing that coming together in the New Year!!

CP have returned my email and confirmed a 686cc 102mm 11.5:1 CR piston.
Kev is pointing me towards this, thank you for your input mate, but I would like a 700cc conversion...

So, I'm going to go with the JE piston kit, a 700cc 103mm 11:1 CR piston. (a Standard bike has 10:1 CR, so this is still a good compression boost.)

I have now ordered it today, and will wait for it to arrive from the USA, so that I can take the new piston and the barrel to the machine shop to get a match.

I am hoping to see gains on my bike of around 10hp..this is my estimate..

My Standard Bike with PC111 44.50HP
With DNA St.3 airbox and CCC 50.00HP (49.01 so far -not been fine tuned)
With JE 700cc Piston 11:1 53.00HP
With a gas-flowed Head 55.00HP

I am hoping that the standard throttle body can chuck in enough air/fuel to make it work properly.

Torque wise, I am looking a similar gain of a total 10ft/lbs.
Torque gains in the low to mid range - is the really important part of the Project for me...

Money-wise for just the 700cc conversion, my estimate,
Spare barrel �60
Machine/ plating �130
Piston kit �115
Top end gasket �37
Bottom gasket �10
Oil sundries �20

Total �372

Now, I am turning my attention to the cylinder head. I am thinking of keeping the standard valves, in order to keep the torque gains to the maximum, at lower revs. I am keeping the Standard Camshaft. Or would bigger valves still give as much gain in low revs?
So, I am looking for a cylinder head.....anyone??

dazmatic · # 7 24-08-10, 17:47

would a raptor head Fit?

richardsracingmad · # 8 24-08-10, 17:51

apparantly the Raptor head wont fit.....I am ringing round Breakers, but they will only sell a whole lump. And I don't want a whole lump, well not another to go with my tuned ZZR x2, ford X-FLOW x3.........I'll be stubbing my toes on it.

By the way..i've had 192bhp out of a ford x-flow (Mk1/11 Escort)...i couldn't keep it in a straight line even with a LSD .....

dazmatic · # 9 24-08-10, 17:54

Doesn't the Capt have some spare bits?

richardsracingmad · # 10 24-08-10, 19:30

No, not any more.....Someone must have a cylinder head.....

I'm looking at possibly adding a +2mm Throttle Body...but I need to understand how it will help my Conversion...I'm not convinced at the moment, as it has been only used on the "big power/ hot cam" conversions.
Has anyone tried one with a standard camshaft?

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