Author Topic: the horrible truth is revealed....  (Read 968 times)

Steve Lake

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the horrible truth is revealed....
« on: October 06, 2006, 08:41:24 PM »
appropo last weekend post (nasty noises from No1 srx) go to the top of the class all those who reckoned it could be piston slap.
Well, it is, sort of.
Just spent a happy couple of hours stripping off, first the rocker cover (everything looked perfect there), then the head, at first glance looked ok, but what's this?
an unhealthily large gap between piston and liner front to back, can clearly see the top ring ! probably a 50 thou + gap!, eased off the barrel, and...oh bluddy dear...
this is now the 3rd time this engine has 'picked up' at the rear of the piston (a not uncommon srx problem, normally associated with poor oil pump performance , or not changing the oil/filter. Now I, if anything, over service this machine, changing the filter with every oil change, and changing the oil VERY regularly, AND, a new oil pump was fitted after the last occurrence ! ) BUT, last time this happened, the bore was honed and appeared to clean up ok, AND i'm running a high compression wiseco piston, with short skirt.
Seeing the state of it, I'm amazed at the compression it still had.
So.....I think this time I'm either going to replace the barrel/liner, or go for a larger liner , say 620cc (denver motorcycles can open out the barrel and press in the larger liner for me, and a new (obviously) piston, maybe high compression, not sure. I wonder if it's worth removing the oil pump to see if it's scored or the seals are sha55ed (it's only done about 18k kilometers), anyway........something to keep me occupied for a few evenings.......anyone got any spares for sale?????
pip pip

themoudie

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Re: the horrible truth is revealed....
« Reply #1 on: October 06, 2006, 10:06:46 PM »
Aye Steve,

Commiserations, same as Sally, except she was on the 634cc bore with the Wiseco HC piston. There just doesn't appear to be sufficient support fore and aft and as soon as it starts to cowp, it starts chewing the barrel.

I understand that the 634 bore is as big as the standard liner will 'go'. The bigger bore requires new liner and boring of the cylinder casting.

I went backwards and returned to 598cc XT liner and 'standard' compression piston, both Wiseco. Renewed seals in oil pump as discussed previous. So far so good!

Also 598cc falls into lower Road Fund Tax band!;-)

If you require part numbers, ask. Obtained mine from Eastwood's, but Norman Hyde may now be sole importer for Wiseco stuff. Denver could supply I suspect.

Not going to Croft this weekend to see the final rounds of CRMCC. Back to work early Monday.

Cheers, Bill


Steve H

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Re: the horrible truth is revealed....
« Reply #2 on: October 07, 2006, 08:00:05 AM »
You shouldnt need a new liner for the 621 piston. Are you running a cooler on your bike ?. Mine without a cooler was running at 120degC+ on the motorway, not good, and I suspect was the main contributing factor to the partial seizure. That said the bike shouldnt really need one. Also in hindsight suspect mine was running slightly weak.


Steve Lake

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Re: the horrible truth is revealed....
« Reply #3 on: October 07, 2006, 01:01:46 PM »
you reckon the sleeve will open out ok Steve?, be good if it could. Yes got the standard grey inport oil cooler on it, and with 2 34mm dellorto's on it, which are running a bit rich, it's not that it's a fuelling problem......interestingly, on the way to cadwell, in the deluge, i looked at the oil temp guage and it was between 80-90......if anything a bit low.
I'm thinking i might get a wiseco h/c piston from that guy in the states (with nearly 2 dollars to the pound, it might be the cheapest option).
Will that make the liner too thin?...does it matter?......lovely day today.....lost without a bike to get out on
pip pip

J Hop

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Re: the horrible truth is revealed....
« Reply #4 on: October 07, 2006, 01:19:23 PM »
Slipstream Tuning in the UK have lots of supermono experience, they seem to favour a 620cc Arias Piston which I'm certain uses the standard liner, give them a call for a quote : Slipstream Tuning, Unit 1,Block 5, Vestry Trading Estate, Otford Rd, Sevenoaks, Kent, TN14 5EL

TEL: 01732 743 248


I have heard people refer to Wiesco as Seizeco

Steve Lake

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Re: the horrible truth is revealed....
« Reply #5 on: October 07, 2006, 01:24:52 PM »
Thanks for that.....just looked at wiseco site, seems i can get a 101 (98 is std 608cc) piston for about £86 ...... + cost of boring the sleve and gaskets
but will try slipstream......all comments greatfully recieved..

Steve H

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Re: the horrible truth is revealed....
« Reply #6 on: October 07, 2006, 05:16:55 PM »
Given the choice I would buy an Arias piston. Also Be careful of C.R. when buying a piston, Ive found the actual (measured) CR to be a fair bit higher than the quoted.

peterj

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Re: the horrible truth is revealed....
« Reply #7 on: October 07, 2006, 09:08:49 PM »
When I was buying a couple of years ago there was nothing available (aus/nz/net) except std and 11.5:1 compression unless you went to a wiseco big bore kit with liner (can't remember the size). I got an 11.5:1 and a long duration cam specced to match the high compression and it works well on 98pulp, but 11.5:1 would be too high for std cam I think. There may be other ratios around now.

themoudie

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Re: the horrible truth is revealed....
« Reply #8 on: October 07, 2006, 10:43:58 PM »
Aye SteveL,

As I said afore "Standard liner bores out to 634cc. Bigger liner only required for max overbore".

Just beware of import duty being added to the value of the item and the VAT being added to the sum total of item + import duty + p&p! The price quoted by Eastwood's was less than this potential total and they had the bits on the shelf. I suspect Hyde's may have this stuff on the shelf as well.

The Wiesco I bought was standard compression 10:1 and is sold for a 'Grizzly' quad, whilst the liner fits all 600's '85 - '92.

Andy230 deals with Slipstream so blether with him as well.

Weather foul here today, heavy showers and blowing a houlie at times!

Cheers, Bill

beeman

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Re: the horrible truth is revealed....
« Reply #9 on: October 07, 2006, 11:04:15 PM »
Mines running on a wiseco 634cc piston and longer opening cam, did have a 620 cosworth hc before but seized.
after taking it apart with the bloke who tuned it you could see it had picked up just like yours had done.
You can still use the original liner up to at least 634cc, well I am anyway!
An idea i tried with mine was to use a slightly wider piston clearance, cant remember what it recommended ? about 3 th I think, this was because the tuner I use reckoned that when the piston got too hot the expansion of the piston may be what is causing seizures. So I bored it out to what the machinist described as a slack 3th rather than a tight 3th rebore. have done about 10k since rebuild and it does clatter a bit when cold but otherwise no problems. (I'm writing this at work and the old srx will now go bang on the way home. almost certainly on the M1 part of the trip)
I'm not the fastest rider in the world, but the bike regularly touch 110 in top and rev it out to the red line with no problems.

sorry to ramble

beeman

PS at cadwell track day the red mist descended and did you know the engine can rev to 9k oops no valve bounce tho' as using heavier springs.

PPS do as I say, not as I do.
We all get Heavier as we get Older because there is a lot more information in our heads

beeman

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Re: the horrible truth is revealed....
« Reply #10 on: October 07, 2006, 11:06:40 PM »
steveL
yes mine is also the 10:1 piston
has noticably less oomph than the 12:1 previously fitted
but soooooooo much more reliable

beeman
We all get Heavier as we get Older because there is a lot more information in our heads

Steve Lake

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Re: the horrible truth is revealed....
« Reply #11 on: October 08, 2006, 06:17:30 AM »
Thanks for all the info guys...... ('spose this should have been in the techie section, will be getting it in the ear from SteveH shortly)

Beeman..........what were the reliability issues about a high compression setup?, i was (3 years ago) running the 11.5 : 1 wiseco on a std cam with a single 400 dellorto, and seemed ok, just tickover was a bit cr*p

I'm not going to bother with Denver Motorcycles (no problem, just no money lol ) I know where they have their re-bore work done, at a specialist engineering company in Ely, so will nip over there and have a chat, they may be able to supply the piston as well.

Now then, if its opened up to 634, what about a gasket?? I see wiseco quote a gasket for this size.....anywhere else ??

looks like another nice day.....grrr

andy230

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Re: the horrible truth is revealed....
« Reply #12 on: October 08, 2006, 08:21:07 AM »
hey steve

sorry to hear the bad news!

FYI, I'd really recommend the Arias piston.  Haven't heard of any nightmares with em (anyone heard otherwise?)

Mine's a 620, a 97mm piston.  Martin Sweet reckons about 10.5:1, higher than quoted.

I know I've had a bit of valve bother recently, but this was due to the decompressor, not the parts or the build.

Good luck mate, let us know how you get on

a

beeman

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Re: the horrible truth is revealed....
« Reply #13 on: October 08, 2006, 10:22:22 AM »
SteveL
Head gasket problems, one non yamaha and the other was a yamaha original.
Could have been other reasons for this but as I use it daily for work coming back to 10:1 seemed like a reasonable move at the time.
The head was skimmed before all the rebuilds started,not so much to raise compression, as to make sure it was flat. Very little was taken off so the ratio was only raised a small amount.
We all get Heavier as we get Older because there is a lot more information in our heads

Steve H

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Re: the horrible truth is revealed....
« Reply #14 on: October 08, 2006, 02:59:02 PM »
Some of the head gaskets sold are solid copper, as apposed to the OE laminated one. Not sure how well the copper works, I would be inclined to fit an OE one and enlargen it if required.