starting to tune the srx

[ram427]

hi to everyone, this is my first post.

want (need!) to tune the srx600 a little and could do with some advice.

increasing compression. is 11:1 too much for a road bike? will the conrod and my leg take the strain or should I stick closer to 10:1 , only really wanted to do a piston swap with a re-bore if required.  what is the max size the barrel can go to without a re-sleeve OR should I go big bore and keep the compression around standard?

exhaust. quite fancy the idea of a carbon fzr400 can on the standard down pipes due to the size (not too big), anyone done this, I guess I'll need to jet up the carbs especially If I swap the filter to  K&N.

On a slightly different theme, the chrome on the forks of my import has seen better days. I have a spare UK spec pair of forks, are the stanchions interchangable (I guess I'll lose the air preload) and are the spring rates the same?

Thanks


Roger

[Steve H]

increasing compression. is 11:1 too much for a road bike? will the conrod and my leg take the strain or should I stick closer to 10:1 , only really wanted to do a piston swap with a re-bore if required. 

The compression the engine can take will depend on the cam, a stage II cam will allow for a higher CR than a standard cam. I'd pitch it at around 10-10.5:1 for a standard cam.

what is the max size the barrel can go to without a re-sleeve OR should I go big bore and keep the compression around standard?

I think 621 is close to the maximum without needing a bigger liner.

On a slightly different theme, the chrome on the forks of my import has seen better days. I have a spare UK spec pair of forks, are the stanchions interchangable (I guess I'll lose the air preload) and are the spring rates the same?

Yep they can be swapped around. Junk the stock spring and fit Hagon or Progressive springs

[andy230]

Yep they can be swapped around. Junk the stock spring and fit Hagon or Progressive springs

I liked the WP progressives in my standard front end.  Pricey, abut £75 plus the extras, but I thought they were better than the Hagons (in my opinion, and weight, and riding style....!)

a

[Steve Lake]

i'm running 640cc at 10.5:1 with twin 34mm dellorto's, (thats the maximum the std sleeve will go out to) with a standard cam, handmade stainless pipes and 'silencer', and 200 quids worth of work on the head (at the cylinder head shop), it is still a very tractable bike, it is geared up one tooth at the front and down one at the back, and will burble along at 85mph on 5k revs with a decent bit of poke still available. forks have progressive springs (not sure whos) with 15 grade fork oil and 10psi preload.  and rear shocks are Koni 'dial-a-rides'...makes for a nice handling nippy little steed....thats #1 srx6

#4 srx6 is the same bore and compression, standard head standard carb but dynojetted, predator downpipes and cutdown predator 'silencer', standard fork springs with 15 grade oil, (no air preload as its a uk spec bike), standard rear shocks, standard gearing.

you know what....it is very difficult to tell them apart performance wise, #4 gets a little bit unsettled if its pushed hard into corners, i put this down to the shocks and springs. (which begs the question why i spent all that time and dosh on #1??)
I guess #4 does puff a bit on a decent hill (not many here in norfolk) whereas #1 stomps everywhere, seems to have more grunt, and the gearing is set to take advantage of that.

On both bikes i have fitted new oil pumps when the rebores were done, it's a bloody expensive job (about 90 quid!!) but if there is the SLIGHTEST wear in the pump seals and ANY visible scores in the pump you will not be pushing sufficient oil out of the journals to splash the bore (especially at the back where it gets hottest) and the end result is your shiny new piston sticks to your shiny new bore, usually in line with the chain tensioner area. and then its gonna cost lots more than a pump would have cost.




both are on Bridgestone Battleaxe BT45's (i've tried others, but always come back to these)

good luck......it's all just common sense really

[themoudie]

To add to SteveL' comments.

I removed the old crusty and worn seals from the oil pump and took the body to an engineer who enlarged the seats to take a 'standard' single lip oil seal as an interference fit and the fitted the seals with a bit of Loctite for good measure. Seal size if remember right was 11mm x 17mm x 4mm. Will check if required. Total cost was ~£6 for seals and £30 plus abuse for the machining. So far so good, about 12K miles.

Maximum capacity with standard liner and with Wiseco piston 11.1 piston is 632cc. The knackered oil seals assured a very rattly top end after 250 miles up the road, with siezure marks on the rear left of the piston and bore behind the timing chain tunnel. Also scored up on the skirt (what little there is of a skirt) as it tried to tip in the bore.

Have reverted to standard bore and piston and a new sleeve. All Wiseco and for the 600 Grizzly, actual capacity is 598cc, cheaper insurance as its below 600cc! Goes well, but probably doesn't have the 'stomp' of Steve's #1 or #4. 80 - 85mph at 5K sounds similar and I'm on 'standard' sprokets.

All the best, Bill

[ram427]

Thanks- always good to get advice from someone who's gone through the pain.

Regarding the hi-comp piston
Sizes from the wiseco website
96 mm (std if it measures up) std comp or 11.5:1
97 mm (1mm over, 621cc ) std comp
98 mm (2mm over, 633cc) 10.5:1
101mm (5mm over, 673cc)  10.75:1 but needs a liner and crankcase work.
 
SteveL, are you running a standard liner with the 640?
 
Presume that there is also #2 and #3. Well done, a man can't have too many toys!!


Thanks

Roger

[beeman]

Hi
My srx is running the 98mm 10.5:1 wiseco piston gas flowed and skimmed head, and stage II cam, one off hand made exhaust (i thought they were all hand made) k&n filters and rejeted. The exhaust uses an end can previously it was a micron carbon fibre but it began to crack with the vibration and my eldest daughter putting a foot rest thro' it. It is now a titanium can by swona.

Progressive springs and konis at the back. also uprated the brakes to take R1 callipers, also has racing clutch fitted.

The bike is pulling 5000rpm at  80mph and runs out of puff (on a Good day) at about 110mph certainly managed the ton up the mountain on the iom. against a standard srx up to 60-65mph not much difference but up the mountain from then on my brother said I was just pulling away and at the top was 1/2 mile ahead.

Dynod at 46bhp and a good flat torque curve from 3k will pull through to 8k no problems (red mist allowing)
on the 8th mile ramsey sprint was running 9.51secs, 76mph terminal speeds. rpm off the the tacho (whoops)

Starting has never been a problem.

Did have a cosworth 620 12:1 piston but one head gasket and a seized piston later had to do another rebore.

Use my bike to go to work on and has been reliable for the last 12k except a weeping head gasket (still)

Having seen Stevel's bikes they certainly look the buisiness

beeman

PS front fork diameter are the same but have different sliders depending on the size of the single disk compared to the twin disc models.