Thumper Club Forum

Technical => Bike Problems/Questions => Topic started by: genawin on September 10, 2009, 03:00:03 PM

Title: SRX 400 OVERSIZE PISTON
Post by: genawin on September 10, 2009, 03:00:03 PM
Hello , I'm looking for available alternatives can anybody advise maybe - xt350 1.5mm o/s (87.5mm) or xt550 (92mm) has anybody got any suggestions ?
thanks Martin.
Title: Re: SRX 400 OVERSIZE PISTON
Post by: CHRIS211083 on September 11, 2009, 04:08:42 PM
HI, why r u after an over sized piston??? has yours seized??? or do you want more power???
Title: Re: SRX 400 OVERSIZE PISTON
Post by: genawin on September 12, 2009, 07:55:25 AM
It has started to burn oil recently - i stripped it to find that it has old corrosion marks in the bore showing that it has stood for some time, i'm not looking for more power in fact i would prefer to keep it standard.
Title: Re: SRX 400 OVERSIZE PISTON
Post by: Steve Lake on September 12, 2009, 01:13:25 PM
you could try having the bore honed and fitting new rings, valve stem seals etc
Title: Re: SRX 400 OVERSIZE PISTON
Post by: genawin on September 12, 2009, 02:35:27 PM
Yes that's good advise i had it honed on Wednesday but the marks are still there so i have put it back together whilst the sun is still shinning ! and i source parts.
Title: Re: SRX 400 OVERSIZE PISTON
Post by: CHRIS211083 on September 12, 2009, 05:53:54 PM
Well......if you dont mind waiting a couple of months i may have a really sweet srx 400 engine up for sale as im gonna fit a 600 motor???burns no oil....returns 95mpg!!!!! with only 21,000km 12,000 mile?
Title: Re: SRX 400 OVERSIZE PISTON
Post by: Steve Lake on September 12, 2009, 07:12:47 PM
just as an aside.....i sometimes run a stock 400 engine in my '6' chassis, only mod is a single 40mm dellorto on a handmade manifold....and to be honest it is a sweet motor....i think it revs better than the 600....not so much poke going up the gears, but top speed isn't far off, just takes a bit longer to get there.
Title: Re: SRX 400 OVERSIZE PISTON
Post by: Sr.X on September 27, 2009, 12:41:38 AM
like the idea of only one carb, any info on the manifold construction?
Title: Re: SRX 400 OVERSIZE PISTON
Post by: jester_parks on September 28, 2009, 05:58:41 AM
XT350 has 19mm piston-pin, XT550 has 20mm!
Sizes of the pistons I can give you  as I`ve got the two pistons at home (and some more) for my own big-bore project!
Title: Re: SRX 400 OVERSIZE PISTON
Post by: mini-thumper on September 28, 2009, 06:53:19 PM
like the idea of only one carb, any info on the manifold construction?

Have just posted an advert in 'For Sale' for a single carb. XT/SRX manifold.

Boyd
Title: Re: SRX 400 OVERSIZE PISTON
Post by: genawin on September 29, 2009, 12:55:47 PM
XT350 has 19mm piston-pin, XT550 has 20mm!
Sizes of the pistons I can give you  as I`ve got the two pistons at home (and some more) for my own big-bore project!
Hello Jester, have you got a piston between 87 and 92mm, i have just bought a xt550 piston from the U.S. (unfortunately damaged) and it has a 22mm gudgeon pin ?
could anyone confirm the srx400 pin size ?
thanks Martin.
Title: Re: SRX 400 OVERSIZE PISTON
Post by: jester_parks on September 30, 2009, 09:23:44 AM
....have you got a piston between 87 and 92mm.....


certainly I have! Will check at home and let you know!
Title: Re: SRX 400 OVERSIZE PISTON
Post by: genawin on September 30, 2009, 01:53:01 PM
....have you got a piston between 87 and 92mm.....


certainly I have! Will check at home and let you know!

I have pulled it apart again and noticed how thin the liner is plus a second look at the bore has pushed me in the direction of new set of rings and keep my fingers crossed as the marks in the bore are minor , i might have a 2nd hone . so if you have some srx400 , xt/sr 500 std or 1st o/s rings please let me know.
Title: Re: SRX 400 OVERSIZE PISTON
Post by: Jez F on September 30, 2009, 04:08:00 PM
Have you considered Triumph (new) Bonneville pistons, theyre 90mm with a 20mm gudgeon pin. I haven't checked the crown height  yet. I bought a pair while I was considering overboring a GN400 and the whole lot is still in a box under the bench.
Jez
Title: Re: SRX 400 OVERSIZE PISTON
Post by: Ian on September 30, 2009, 09:01:49 PM
Photo included of Standard SRX-4 piston/barrel
Ian
(http://i193.photobucket.com/albums/z24/ian650/P1020747.jpg)
Title: Re: SRX 400 OVERSIZE PISTON
Post by: jester_parks on October 02, 2009, 06:07:43 AM
SRX pin -size: nobody got an idea?
I`ve got several pistons suitable (what diameter is concerned)...but pin-size is VITAL!!
Title: Re: SRX 400 OVERSIZE PISTON
Post by: genawin on October 02, 2009, 02:21:19 PM
SRX pin -size: nobody got an idea?
I`ve got several pistons suitable (what diameter is concerned)...but pin-size is VITAL!!
Hello Jester , i posted that i have pulled it apart again and decided to try a 2nd hone with new rings.
thanks for your help.
Martin.
p.s.the pin is 20mm.