Author Topic: Project SRX non progress  (Read 1465 times)

leah

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Re: Project SRX non progress
« Reply #15 on: July 29, 2010, 08:35:16 PM »
He remains Rex cos he WILL be king!! Not yet tho as I'm still struggling: another carb clean with new main & pilot jet plus all the other goodies you get in a carb refurb kit. Float height checked and fuel definately getting to plug (backfires indicate that fuel getting thru no?) Then there's the new coil, plug cap & iridium plug. Nothing except backfiring so I now checking valve clearances & decomp cable adjustment as per the manual. Thing is when I get the T mark aligning with the pointer it wont stay there, just flips round a bit. The only way to keep it there is by physically holding the spanner turning the crank. Is this right? Is the timing a bit out? I'm lost here as other bikes I work on are 2 stroke twins where TDC can be found and the crank stays put! The plug is out on Rex incidentally so there's no compression fighting the piston.

interested in any coimments and help here & realise I'm probably being dense... :-[

themoudie

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Re: Project SRX non progress
« Reply #16 on: July 29, 2010, 10:16:16 PM »
Aye leah,

Reads as though the timing is 'out'!

To make things easier, put a piece of 6mm rod through the hollow back axle and raise the back end on two axle stands, or else use a paddock stand. Engage 2nd or 3rd gear and turn the engine over using the rear wheel, checking until you reach the desired 'T' mark with the piston and cam in the correct positions. BE CAREFUL THAT YOU ARE NOT 180 degrees OUT! ??? ??? ??? You can then lock the back wheel in position by applying the rear brake and tying it down! You will still have backlash in the gearbox and primary drive to contend with, but it won't 'flip' past the 'T' mark, as at present.

Others may have better ways of doing it than me, and if SteveH or SteveL come along and offer a method different from mine, which appears easier, USE IT!  8) 8)

I hope REX will soon run and perform, rather than remaining as a petulant brat!

May perseverance prevail.

My regards, Bill.

leah

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Re: Project SRX non progress
« Reply #17 on: July 30, 2010, 01:54:08 PM »
Hi Bill, thanks very much. Don't see why your method shouldn't work as the back brake works at least! Just to make sure I've got my 4 stroke cycles right, the compression stroke is the upward one compressing the fuel/air that came in on the intake stroke. Therefore on this stroke all valves closed right? If 180° out some valves would be open & you wouldn't be able to check clearances as there wouldn't be any?
So for clearance checking the flywheel must be dead on that mark? If the valve timing was out, how would I know? I didn't assemble the head and valvegear as it was already on. Got a horrible feeling I need to remove the LH engine cover to check camchain marks... :(
Anyway I'll have a look tonight.

Regards

Leah

Steve Lake

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Re: Project SRX non progress
« Reply #18 on: July 30, 2010, 08:47:19 PM »
what i do is..........take the plug out, stick a pencil down the 'ole, (a long pencil, so's when/if you let it go it won't disappear!)
turn the engine over slowly until the pencil tells you you are at TDC, then check valve clearance, if there is clearance on all 4 valves you are at TDC on the compression stroke, no clearance?...turn it over one more 360deg, check clearances again.....if you still havn't got any clearance then you have an issue with the cam/chain positioning..... the clearances i use are 3 thou inlet, 6 thou exhaust...a sort of midway setting.

in my experience (i am using high comp pistons, not sure if this is true for standard comp) if the timing is out by a tooth or 2 on the camwheel, then you'll feel the piston touch the valves........

Steve Lake

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Re: Project SRX non progress
« Reply #19 on: July 30, 2010, 09:15:09 PM »
and another thing......

I do have a carb you can borrow......it's a single 42mm dellorto with accelerator pump, on a handbuilt manifold....the main thing is....it works......was on my srx6 for several years........until i got a matched pair of 36 mm dellorto's off fleabay which fit original inlet pipes.

you won't be able to use this on the road...'cos you have to bash 10 bells out of the base of your tank to make clearance....BUT....with a plastic bottle and pipe tied to the cross bar (with your tank removed) then it'll work fine....no choke.....blipping the throttle pumps xtra fuel in.

not only that.....

I have l/h cover with generator coils and ignition pickup

you are welcome to borrow both to try and resolve this problem.

Steve Lake

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Re: Project SRX non progress
« Reply #20 on: July 30, 2010, 09:33:03 PM »
thinking about it.....

I sold one srx6 i'd built... to a plumber friend of mine....at half price.....and got a full central heating system fitted (no i'm not suggesting you flog rex to a plumber :D )

but......after about 20k miles he decided to strip it all down and 'tart' it up a bit...all was fine and he completed another 10k miles then started to experience difficult starting....and finally...no starting....

he bought it over to me in his van and i went through everything.....got it rebored, nice new h/c piston, got new valve seats fitted, rebuilt it and set the timing up......and the bu55er still wouldn't start....odd backfire (it was running on a pair of mikuni 34mm carbs, which i tried on my bike just to make sure they were working) a few pops and wheezes....all this time i was checking that i had a spark....

i ended up sending the generator away for testing (normal resistance testing showed it to be ok) it proved to be a winding breaking down (the high voltage tester is called a 'wee megga', i know you were just dying to know that)....once repaired....also got a new pick up, everything then became wonderful!

just a thought


themoudie

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Re: Project SRX non progress
« Reply #21 on: July 30, 2010, 09:39:30 PM »
Aye leah,

I am sorry for the delay in replying and my thanks to SteveL for stepping into the breach.

"Just to make sure I've got my 4 stroke cycles right, the compression stroke is the upward one compressing the fuel/air that came in on the intake stroke. Therefore on this stroke all valves closed right?" YES

"If 180° out some valves would be open & you wouldn't be able to check the open valve's clearances as there wouldn't be any?" YES

If the cam/valve timing is out by 180deg, the valves won't touch the piston, but the spark will arrive with no compression on the inlet or exhaust stroke!  ???

As SteveL says "if the timing is out by a tooth or 2 on the camwheel, then you'll feel the piston touch the valves........"  ??? But I don't think that is your problem or else the engine wouldn't have turned over/ you'd 'ave heard a 'dink', as valves touched piston!  ???

Before you strip bits of engine cover off, are you sure that the electrickery bits are all 100%???????? I will send the 'Ignition' section from the Yamaha workshop manual, by mail attachment, for you to use.

Sorry not to be of more help and I hope others will help if they can. Or 'SHOUT' if I have made an error!

My regards, Bill.

themoudie

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Re: Project SRX non progress
« Reply #22 on: July 30, 2010, 09:41:54 PM »
Aye leah and Steve,

That last post of Steve's is where my head is going as well, as you can see from my immediate previous post about circuit diagrams. Will still send pdf under separate post.

Regards, Bill.

leah

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Re: Project SRX non progress
« Reply #23 on: August 03, 2010, 09:41:25 AM »
Thanks again guys.  Bill - I got the ignition info so will attempt to check the generator out.

Steve, many thanks for the offer of carb and generator. If I can't resolve this problem I would be glad to borrow them...just can't believe this is being such a hassle :o

Sr.X

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Re: Project SRX non progress
« Reply #24 on: August 12, 2011, 01:00:53 AM »
Unsure about pilot jet and pilot screw details. Pilot jet has a hole through it and goes in snug. Pilot screw needs to be backed out a certain number of turns. My pilot screw was backed out 1 3/4 turns when I got the bike and thats where I set it after the carbs were completely cleaned and re-assembled. It started on the second kick and ran fine but I don't know anyone with an SRX 400 to ask questions of so I'm kind of running blind. Any info on the pilot screw and how to reach it would be appreciated. I'm up in northwestern British Columbia, Canada and most people don't know what make or model my bike is. Love this site, love those thumpers.