Kent cams and Busa pistons.

[lawson17]

I have managed to get hold of some kent cams and busa pistons for a reasonable price, the cams are already fitted to stock SV sprockets and I'd like to also remove a layer from the head gasket... Unfortunately she still has stock headers and just a slip on at the mo. I have been on the hunt for system, but not much luck so far.

I'm hoping this will gain a bit of HP, without her getting the 'ump and spitting bits all round the place.

A dyno run would be nice afterwards, but would it be safe to run after the mods for a short while?

[jambo]

Fit the cams, you've got them, it'd be rude not to.
As for the thinner head gasket, I think generally people tend to skim the head instead, but either way I'd expect no real improvement without advancing the ignition.
You'd want to do this at the same time as fitting the alternate pistons which would require a very light rebore I believe.

All in all the cams would probably make the most difference, and are the easiest to do :)

Jambo

[suzukigt380paul]

dont think the busa pistons will add any hp,although they are forged pistons and are stronger and will take more abuse then your sv will ever give them

[squirrel_hunter]

I ran 'Busa pistons and a cam swap for a bit before the crank grenaded, unrelated to the mods I'd say.

For the pistons its a 0.0002 inch over bore from what I remember but don't quote me on that as I can't find the mesurement. I had Piston Broke Engineering, Bristol (0117) 9412300 do the work for me, Steve will know what to do. You will need new SV rings though.

The head gasket mod is something I didn't do that time, will do the next. Basically take the middle metal bit out from the gasket.

As for HP, I didn't do a before and after dyno run. I will next time. But my bum dyno dectected a nice little increase. Can't say if it was the cams or the pistons or both. Either way do it.

Out of interest which Kent cams do you have and what model SV is it?

[lawson17]

Thanks for the replies.

It's a K3, and SUZ43 cams. Jus in the process of stripping it all down now. Hoping to get it all back together by next week. Then off to he dyno. I'll put up a copy of the results. Although I don't have a direct 'before' comparison, it was making 68hp on the bemsee dyno.

[m1tch_1987]

If the cams are for the FI model of engine I might be interested in them, I currently have the carb model and I know that those will drop straight in, let me know if you want to sell them.

[lawson17]

Hi Mitch,

Sorry mate but they are already spoken for... :(

[m1tch_1987]

Hi Mitch,

Sorry mate but they are already spoken for... :(

Ah, no worries, I will look forward to seeing what the cams are like as I know there isn't a huge amount of headroom for extra power before the crank gives up lol

[yorkie_chris]

Fit the cams, you've got them, it'd be rude not to.
As for the thinner head gasket, I think generally people tend to skim the head instead, but either way I'd expect no real improvement without advancing the ignition.
You'd want to do this at the same time as fitting the alternate pistons which would require a very light rebore I believe.

All in all the cams would probably make the most difference, and are the easiest to do :)

Jambo

Curious to know why you think ignition advance would help?

I slotted my pickup and noticed no difference with couple of degrees. If you did both increase comp and more advance you would increase chance of knock.

It might be worth to check piston to valve clearance before you start reducing head height with these more aggressive cams.

Taking middle layer from gasket is fine way to increase comp, think it is about 15 thou thick from memory but it's been a while.

I ran 'Busa pistons and a cam swap for a bit before the crank grenaded, unrelated to the mods I'd say.

For the pistons its a 0.0002 inch over bore from what I remember but don't quote me on that as I can't find the mesurement. I had Piston Broke Engineering, Bristol (0117) 9412300 do the work for me, Steve will know what to do. You will need new SV rings though.

The head gasket mod is something I didn't do that time, will do the next. Basically take the middle metal bit out from the gasket.

As for HP, I didn't do a before and after dyno run. I will next time. But my bum dyno dectected a nice little increase. Can't say if it was the cams or the pistons or both. Either way do it.

Out of interest which Kent cams do you have and what model SV is it?

2 tenths? You sure it is 2 tenths not 2 thou?

[jambo]

Curious to know why you think ignition advance would help?

I suppose mostly when I've seen people go down this route they've done one, other or often both. Both modifications do increase the chance of knock, but I'm not sure how far you can go with UK 95 RON fuel and still be happy without reaching for the super unleaded.

Jambo

[yorkie_chris]

The amount gained from the advance on the SV is minimal, I think it's already up there in terms of risk to gains on that adjustment.

A lot of people got offset timing keys and such thinking well it cost money it must help.


I think zoran did a bunch of dyno tests, found very limited to no gains from it, apparently he sometimes uses the offset timing keys backwards to retard it a bit on seriously built engines.


Increasing comp on the other hand is guaranteed by basic principles to give you a bit more hoof. :)

[SV650Racer]

^ ignition does very little on the SV. Compression and squish combined with the right cams and pistons is most important. If you can afford it lightening and balancing the crank is worthwhile, takes the stress off the end of the crank and allows the engine to rev freer. You can easily loose 1kg from the cranks weight.

[yorkie_chris]

How does lightening the crank (presumably the webs) reduce stress on the end? I can see how lightening the flywheel (easy) can do this.

[SV650Racer]

It just reduces the overall spinning mass of the crank - thus reducing the amount of weight being spun on the flywheel end. On its own it helps and have run many tuned bikes with just this and have not had one crank failure. Its also recommended to lighten the flywheel as thats the most critical part that causes the stress on the crank, you can do it either way. The bike will also rev quicker which results in a more responsive engine with no loss of torque, obviously you can go too far.

Plus the balancing to match pistons and rods if changed is more than worthwhile. I rode a bike where this wasnt done and the vibrations were very noticable.

Its not cheap though and obviously means a total strip down so for most people just playing with top end work its not really worth it.

[yorkie_chris]

It just reduces the overall spinning mass of the crank - thus reducing the amount of weight being spun on the flywheel end.

If you're just reducing the weight of the middle, having the engine accelerate faster will try and spin the flywheel up faster, meaning more torque transmitted through the weak bit.
If anything a heavy crank will reduce stress on the flywheel end.
A lighter flywheel helps both ways, and should put you back to where you started in terms of reliability if you made it spin faster.

I'm just curious to know if you think the crank failures are a result of net changes in crank speed, i.e the engine spinning up or slowing down. Or the sort of changes in speed looking at it more closely, i.e as the crank speeds and slows in between firing and compression cycles etc.


I machined flywheel and some other rotating bits in there. It was very noticeable in the peppiness of the engine. I did sums and it was in region of tens of kilos of equivalent mass reduced from the whole bike in lower gears. Very very cheap performance increase :)

[lawson17]

I bought a secondhand flywheel, which I removed three magnets from and turned it down where possible. Is it necessary to have it balanced afterwards? I can do it statically, but that might be a bit different to when she's whirling around on the end of the crank!

[yorkie_chris]

I didn't bother. I didn't notice any vibration. Then again I clocked it within about 3 10ths when it was done. The magnets should be similar so any dynamic imbalance should be minimal. I'd have a look at the static balance though.

Obviously your choice, I was doing this to a 90,000 mile engine I didn't expect to last that long anyway!

[squirrel_hunter]

For the pistons its a 0.0002 inch over bore from what I remember but don't quote me on that as I can't find the mesurement.

2 tenths? You sure it is 2 tenths not 2 thou?

What did I say about quoting me?

0.002" is what it should be, two thousandth of an inch.

Or 0.0508mm using google convert.

Or 0.00412371wlc (Worlds Longest Cat is a recognised standard unit of measurement).

[SV650Racer]

I bought a secondhand flywheel, which I removed three magnets from and turned it down where possible. Is it necessary to have it balanced afterwards? I can do it statically, but that might be a bit different to when she's whirling around on the end of the crank!

Wouldnt worry about that.

So far no crank failures on tuned engines with lightened and balanced crank running either stock genny or lightened flywheel or full race genny.

Had 5 in total even on stock engines running stock crank.

The big plus from it as said is the response from the engine.

[lawson17]

Nice one, thanks guys (and girls Sarah!) :)

Right the next pickle, installing the rear ex cam, looks as though the sprockets might be mounted wrong? unless I'm being a spud. Put the intake in first, with line parallel to head. 16 pins to the '3' mark on the ex cam, but the line is not parallel to the head! The front went in lovely. (both marks paralell on each cam)

Do I just jump one tooth on the ex cam to make it right? (so it would be 15 pins) Or have i missed something really silly?

I have attached a pic...

[lawson17]

I guess the most important thing is the lines on the end of the cams being parallel to the head? As the sprockets are identical in size etc.

They are all definitely in their right locations. I have triple checked now! :)

Comparing it to the stock cam I took out, it is pressed in slightly differently. Unless this is part of the idea? But the front is looking good...

[yorkie_chris]

If you are looking at teeth and markings the only thing that can make that difference is stretch in chain. Or not having exactly TDC...

[lawson17]

The stock cams all line up fine... So the chain is good. I'll measure to make sure though.

:)

[lawson17]

The chains measure the same, over the same distance, jumping one tooth just as a trial still didn't make the lines quite parallel. If I'm right, the rears should be installed at 90 deg ATDC?

Maybe that's why they were cheap! :)

[yorkie_chris]

The only possible reason for this is the etching on the sprockets is a bit out.

Are you sure they're the same sprockets? Should be 3 and 4 stamped on them IIRC, there is a number somewhere that ID's them.


Are you starting from scratch timing this up?

[lawson17]

It's supposed to be a straight cam swap... The guy I got them from pressed them on for me, as they were fitted to APE sprockets. They have also had a run of mig put on them...

Comparing to the stock cam, this troublesome one is out by 1.5 teeth on the chain wheel. It's almost there by jumping it round 1 tooth. But still not parallel.

The markings / sprockets themselves are identical to the stock ones. Same sprockets fitted to both in and ex on stock cams, just pressed on in different locations. 19F sound about right?

[yorkie_chris]

How did he time the cams to the wheels?

Plus it depends how kent did these cams, depending on profile it's not 100% necessary that the timing stayed exactly the same.


Presuming that a) kent knew their business and b) so did whoever put the sprockets on and they were both singing from the same hymn sheet... I would time them based on the sprocket markings.

[lawson17]

That's what I thought... But the only reason I'm hesitant is that the front is spot on....

Nothing fouls turning over by hand, but doesn't mean much...

[yorkie_chris]

I would check with maker of cam.

Maybe with how they add weld and grind back it is not certain where original cam lobe center was.

[lawson17]

Just heard back from Kent, they regrind, keeping the original lobe centres. Hmmm...

[lawson17]

Now then... Here's an idea... Whether its any good or not?

Keep the kent intake cams in there. As they seem to be right. And put carby intakes in the exhaust side? (I have set in t'garage)

What do you recon?

[zadar]

It's supposed to be a straight cam swap... The guy I got them from pressed them on for me, as they were fitted to APE sprockets. They have also had a run of mig put on them...

Comparing to the stock cam, this troublesome one is out by 1.5 teeth on the chain wheel. It's almost there by jumping it round 1 tooth. But still not parallel.

The markings / sprockets themselves are identical to the stock ones. Same sprockets fitted to both in and ex on stock cams, just pressed on in different locations. 19F sound about right?

Pressed sprocket on using eyeball? :)
All 4 sprockets are same, like you said they just pressed in different location.