Seeley (replica) Framed Project Road Racer

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Zunspec
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Zunspec » Thu Aug 29, 2013 12:11 am

Hi SD,

I'm also a member of the broken Scaphoid club :D . Oddly enough the last time I raced at Snetterton, here's hoping I don't repeat the performance.

Cheers Geoff

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Zunspec
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Zunspec » Mon Mar 10, 2014 5:46 pm

I took the Seeley to a Llandow track day on Saturday, great weather and the Seeley went well. A good deal of progress was made on engine and chassis set-up, mostly thanks to my new tame international standard rider a Mr Gary May and his dad. Much twiddling went on with suspension at both ends and I think I now know why the engine holed a piston at Snett last September. Something as simple as an inadequate breather hole in the tank cap, it was not up to the job of compensating for the prodigious rate that a 2-st with 38mm carbs can drink fuel at full bore. The fuel starvation causing a v/weak mixture and bang went the piston. Subsequently rectified by going at the breather hole a with small screwdriver :D

Image Image Image

A short video clip, Gary leading these bikes

http://www.flickr.com/photos/zunspec/13061748143/

What a test day is all about.

Cheers Geoff

scotduke
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Re: Seeley (replica) Framed Project Road Racer

Unread post by scotduke » Tue Mar 11, 2014 12:12 am

It looks great Zun - glad you've got the problem sorted and there won't be any more holed pistons.

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Hooli
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Hooli » Tue Mar 11, 2014 11:13 am

What an annoyingly simple fault to kill your engine, I'm kinda surprised it didn't show up on dyno runs tbh.
Classics ain't built in Metric

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Zunspec
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Zunspec » Tue Mar 11, 2014 7:09 pm

Hello Hooli,

When performing a dyno run you are only on wide open throttle (WOT) for brief periods, say 5 - 8 seconds, Just enough to run the engine up to max revs and not long enough to drain the float bowls. On a circuit you are giving WOT almost all the time and at the end of a straight the bowls must have run out.... kerpow. Running a drain test, bike on the paddock stand, into a jug does not seem to have the same effect as I suspect air is going in via the open fuel tap, hence fooling you into thinking all is reasonably OK. You are right a bloody simple problem cost a bunch of dosh.

On the bright side we seem to have solved the problem and I am making modifications for a fool proof (if there is such a thing :D ) breather arrangement. Mr May was going like a very fast thing going very fast on the last session of the day, there were a few Blades & R1s thinking "whats this noisy thing behind, sh1t it's gone past me". OK there is no decent straight for the 1000cc bikes to get it on at the top end at Llandow but the bike/rider combination has a few bods in the CRMC 500AC class thinking they will have a serious rival this season. Gary's s has got his ACU licence re-newed, CRMC membership done and we hope he can get an entry for Pembrey on the 19/20 April. The proof of the pudding will be revealed on race day 8-) .

Cheers Geoff

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Hooli
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Hooli » Tue Mar 11, 2014 7:49 pm

I've watched a few dyno setups being done Zunspec, including my 14. I'm aware they aren't on full throttle for that long when it's done. I guess it depends on how marginal the problem was, if it was very bad it'd have shown up, but just a bit dodgy wouldn't have shown.

I wonder if you can calculate the size of the breather needed by looking at the max flow rate for the carbs?
Classics ain't built in Metric

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Zunspec
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Zunspec » Tue Mar 11, 2014 8:51 pm

Evening Hooli,

A piece of corroborating evidence is that when it stopped at Snett. it was dead on both cylinders (same as happened at Llandow). OK, RH side had a big hole in the top but LH side should have performed as a single cylinder 250. The RH squish was a bit tight (too tight) which probably caused that side to hole with the weak mixture, there was no sign of any damage on the LH side. At WOT a 2-st gets through a lot of fuel when breathing through a 38mm carb. On my original Seeley T500 I estimated that it was only getting 12-14 miles per gallon when racing, races were only 8-12 miles long so no real problem.

The breather hole in the Monza cap was only about .75mm dia We have opened it up to approx. 3mm and the problem seems to have been cured.

Cheers Geoff

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DAM
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Re: Seeley (replica) Framed Project Road Racer

Unread post by DAM » Wed Mar 12, 2014 12:43 am

I'm tempted to come and see it race, let us know when you are out with it again.

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Zunspec
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Zunspec » Wed Mar 12, 2014 1:01 am

Hiya DAM,

CRMC race dates for 2014. Open pit area, food and drink available at most circuits etc. You can always cadge a hot cuppa from my pit though.

Cheers Geoff

April 19 + 20 Pembrey
May 17 + 18 Lydden
June 13 +14 + 15 Anglesey (Track day on Friday)
July 5 + 6 Brands Hatch
August 8, 9 + 10 Donington Park Classic Festival, 3 days of bikes, displays and racing
September 6 + 7 Cadwell Park
October 11 + 12 Snetterton Race of the Year
Last edited by Zunspec on Wed Mar 12, 2014 6:25 pm, edited 1 time in total.

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Hooli
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Re: Seeley (replica) Framed Project Road Racer

Unread post by Hooli » Wed Mar 12, 2014 4:16 am

Zunspec wrote:Evening Hooli,

A piece of corroborating evidence is that when it stopped at Snett. it was dead on both cylinders (same as happened at Llandow). OK, RH side had a big hole in the top but LH side should have performed as a single cylinder 250. The RH squish was a bit tight (too tight) which probably caused that side to hole with the weak mixture, there was no sign of any damage on the LH side. At WOT a 2-st gets through a lot of fuel when breathing through a 38mm carb. On my original Seeley T500 I estimated that it was only getting 12-14 miles per gallon when racing, races were only 8-12 miles long so no real problem.

The breather hole in the Monza cap was only about .75mm dia We have opened it up to approx. 3mm and the problem seems to have been cured.

Cheers Geoff

It only occurred to me after I'd posted that a dyno run wouldn't be at WOT long enough to empty the float chambers, hence the problem only occurring on the track. It definitely sounds like you've tracked it down properly, I just like running through problems in my own head to learn etc.


It was DAM asking about racing dates btw :)
Classics ain't built in Metric

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