Aye Stuebydoo,
Welcome to the forum.
I've ridden an SRX 600 for the best part of 16 years now. Current machine (Sally) has McCrane footrests that are set further back and higher than the standard footrest position and standard clip-on bars mounted on the stanchions above the top yoke. I'm 6'2" in socks and weigh in at ~13½stone. However, I was up to nearly 15 stone at one point and still fitted fine. There is no size difference between the 400 and 600 twin shock model frames. However, there are different wheel diameters that do affect the seat height. I am renovating a butchered SRX Monoshock 400, with XT600E motor fitted at present and this has 17" diameter wheels front and back and also a different frame and ride height. Again there is no difference in the frame/seat/bars relationship between the 400 and 600 monoshock models.
On both frame types I can get my feet flat on the deck, a touch of "numb bum" after 150 - 200 miles and the bars could be raised an inch or two if you are doing a lot of riding below 50mph. Sightseeing!
Above this the wind pressure lifts the weight off the wrists, for me.
The 400 motor has plenty of power, yet may lack some of the torque of the 600. It is a smoother running motor and more economical mpg, but hardy, providing you warm it through afore large throttle openings. DO NOT 'PLONK' these motors!!!!
They may be called "Thumpers", but they are not long stroke singles like AJS/Matchless, Norton ES2/19S, Panther 100/120, they like to be revved and sitting in a high gear 'plonking' about will knock the bearings out of the motor and especially with the 600 engine shred the 5th gear/pinion pair!
This requires a complete engine strip, rebuild, with new bearings, gear/pinion pair, oil pump, seals and anything else that you may find worn. This may cost £1,000 + labour, if you entrust it to somebody else!
Plenty of clean semi/synthetic 10/40 every 2,000 miles/3,000Km and a filter change every 4,000 miles/6,000Km, should keep the motor in good fettle. Sally is now up to 120,000Km, with a complete strip and rebuild 70,000Km ago.
The bikes are slim, very maneuverable and the monoshock is said to have an improved ride over the twin shock, but I have yet to experience this. The Koni's on Sally I have found to be very compliant.
Another word of warning is to check for welding/fibreglassing around the base of the petrol tank 'panniers', especially on the lefthand side as this is where condensation or degrading ethanol lie and rot the bottom out of the tanks. Replacements are available, from Japan, repair is not cheap and if there is any sign of rustiness in the fuel or tank after giving it a good shake, look for a substantial discount or elsewhere.
There are others on here who will no doubt add their twopence worth
and you can also try entering "SRX" in the 'Search' box in the top right hand of the forum screen, when you are in the various pages of the forum. Another site you should visit is SteveH' website:
SRX600_HomepageOn Steve's website you will find a host of useful articles, parts microfiche etc, along with a rake of images from all over the world of SRX's.
If you have any further queries or just want to look in from the side, enjoy the forum.
Good health, Bill