Cams vs Big Bore

[scotgary]

Hi Guys.

My 1100 Katana project is coming along nicely. I have a brand new set of OEM 72mm pistons and rings that I was going to install.

I have come across a Wiseco 1166 kit at a very good price, and also a set of Yoshimura ST-1 cams!

If I could only afford one, which should I choose?

 

The bike is a street bike that will not see the drag strip. I currenly has Mikuni RS36 carbs and a Motogpwerks exhaust.

Also, what is the correct deck height, and how much can I safely mill the head for extra compression if I use the OEM pistons?

 

Thank you

[Fazz711]

I would go big bore on a street bike. 

Edited October 16, 2018 by Fazz711
Spelling

[KATANAMANGLER]

For me head work with cams trumps a wiseco kit alone.  Cams alone, I don't know. 

You could fit slotted cam sprockets on the standard cams and dial them in. I think the standard on these is about 109 exhaust and inlet.. I had mine at 106  inlet and  108 exhaust with a wiseco kit and RS36s and it went well compared to stock.

The wiseco kit will make a difference on it's own but not as much as it will without some cam and head work.

The lumpy cams might not be as useful on a street bike.

[johnr]

havent you got a spare kidney you can sell?

[Duckndive]

no substitute for cubic inches   cc s

[Duckndive]

But in all honesty you would most likely gain as much by just blue printing the stock motor

 

Edited October 16, 2018 by Duckndive

[johnr]

though the reality is that per pound speent, an improvement in times on the track is more likely to be achieved by a good set of tyres and a couple of track days than a load of engine work. not that anyone wants to hear that.

[R1guy]

4 hours ago, scotgary said:

Hi Guys.

My 1100 Katana project is coming along nicely. I have a brand new set of OEM 72mm pistons and rings that I was going to install.

I have come across a Wiseco 1166 kit at a very good price, and also a set of Yoshimura ST-1 cams!

If I could only afford one, which should I choose?

 

The bike is a street bike that will not see the drag strip. I currenly has Mikuni RS36 carbs and a Motogpwerks exhaust.

Also, what is the correct deck height, and how much can I safely mill the head for extra compression if I use the OEM pistons?

 

Thank you

Need a photo of this bike please

[gs7_11]

For the road, I feel the benefit of a big bore kit every time I ride.

Cams, I only felt when I was in the mood to cane it. Most of the time they made the bike less good to ride. I've taken my Kent race cams out and sold them.

Edited October 16, 2018 by gs7_11

[wraith]

2 minutes ago, gs7_11 said:

For the road, I feel the benefit of a big bore kit every time I ride.

Cams, I only felt when I was in the mood to cane it. Most of the time they made the bike less good to ride. I've taken my Kent race cams out and sold them.

+1 on that

had my old GS1000 bored to 1148cc ( using gp z 1170 piston ) and had a set of Anderson S3 cams and CR35 carbs, the cams grate for top end end and riding like a di#k on the street but the big bore was much more fun and usable for the road.

[VJ]

Id go for bore purely because then you only build the engine once and take the lid off later when you decide you want the cams aswell. If you do cams first its another top end build to put the big bore slugs in at a later date.

[arnout]

8 hours ago, scotgary said:

..

Also, what is the correct deck height, and how much can I safely mill the head for extra compression if I use the OEM pistons?

Deck height depends on the thickness of the head gasket and so also the squish that you want. Do a dry assembly first to measure the piston to head clearance (plasticine), and go from there. Base gasket(s) can be used to adjust the deck height.

Milling the head is only limited by the valve (seats).

[Reinhoud]

Go for the big bore, big change the hot cams don't work with the stock CR and make the bike slower instead of faster. No clue what the CR of your bike is by the way.. 

[Gixer1460]

Going from 1127 to 1186 picked up 20hp for me and shed load of torque - difficult to get that increase with cams and not change anything else!

That was as back - to - back as I could do - everything stayed as was, except the jetting!

[CockneyRick]

16 hours ago, gs7_11 said:

For the road, I feel the benefit of a big bore kit every time I ride.

Cams, I only felt when I was in the mood to cane it. Most of the time they made the bike less good to ride. I've taken my Kent race cams out and sold them.

I know, i bought them  Already Roger U. big bored, so i'm going both  

[TLRS]

I suppose Yosh cams are racy, which suggest they could sacrifice midrange punch. Are there no figures or sheets about to get an idea what they'll do with a similar configuration?

What riding style do you enjoy most, riding the wave of torque or wringing it's neck?

[nlovien]

On 10/16/2018 at 8:18 PM, Duckndive said:

But in all honesty you would most likely gain as much by just blue printing the stock motor

 

 time spent getting a tired set of valves back sealing properly + setting the squish up properly then dial in the std cams - playing around the 105/105 to 110/105 range to find yir happy range

focussed cams can end up costing a shit load more than the cam itself - typically means there is more HP but at the bequest of more rpm - and more rpm likes things like underbucket shims - lighter valve bits, maybe better valve springs - sometimes better rod bolts or even new rods, then you be as well lighten the crank - are we over a grand yet ? 

big bore always provides from zero to redline so if its just one thing without incurring add on bits to make it work then big slugs win - spend on selecting a trusted company to bore it for you - the down side to a big bore kit is a cowboy machine shop - and - again, get the squish right via headgasket selection after decking the pistons to the block - i.m thinking ( needs confirming !) 0.040" squish for these motors ???

[scotgary]

I totally agree. I have decided to use the new OEM piston and rings with a degreed stock cam.

I still need to get confirmed specs for deck height. Are the pistons supposed to be 0.40" in the hole at TDC, or flush to the top of the cylinder?

 

[Gixer1460]

1 hour ago, scotgary said:

I totally agree. I have decided to use the new OEM piston and rings with a degreed stock cam.

I still need to get confirmed specs for deck height. Are the pistons supposed to be 0.40" in the hole at TDC, or flush to the top of the cylinder?

 

Hope you meant 0.040" as nearly 1/2" down the hole won't help!  Subject to your head gasket thickness the deck ht. varies - for max output vs reliability the squish should be between 0.75 - 1.0mm - tighter is better but rod stretch and over-reving will lead to contact.

[scotgary]

Sorry, massed a Zero, I meant 0.040 inches down. Everything I can find says the piston crown should be flush with the top of the cylinder liner...that is zero deck height or squish.

[Jaydee]

As Gixer1460 said, squish depends on the head gasket thickness. I've always set up my squish at 0.9mm (0.035"). For example, if my head gasket is 0.6mm thick (0.9mm squish minus 0.6mm gasket) then I know the piston must be 0.3mm below deck height.

[arnout]

Yup, what Gixer1460 and Jaydee (and myself) said.

I've tried a squish as low as 0.60 mm once, but marks on the head later showed this was not enough to allow for conrod stretch.   I believe the manual states 1mm for squish (but may have read it somewhere else), which is the minimal value for the squish effect to work properly.

I suggest reading up (Google) on the subject if you do not fully grasp what's been said here.

[Gixer1460]

Its the edge of the piston that determines the squish not the crown - if the crown is level with the gasket surface you'll be losing power through a bad burn / combustion. The edge should be closer to the gasket - a bit of solder placed on the piston edges in some grease during a dry build with a used gasket will reveal what it will be - ideally as noted above

[Reinhoud]

Do con rods stretch that much?!!

[Gixer1460]

1 hour ago, Reinhoud said:

Do con rods stretch that much?!!

I don't know but top engine builders won't go below 0.5mm squish for a reason! A rod in a super hot race engine @ 12,000 rpm could easily stretch / use up all the bearing clearances that total 0.5mm?