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Project Yamaha SRX 250 Cafe Racer

Discussion in 'Your 250cc Projects' started by Andych, Oct 9, 2016.

  1. Andych

    Andych Well-Known Member Premium Member

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    Well, looks like the 250 engine is getting a top end overhaul with the stock barrel and piston ( new rings ) and reco head from my original engine.
    I dropped the 350 barrel of to be bored.... $88 for bore approx 1mm, hone and deck...I don’t know if that is good or just going rate...but it suits me fine..
     
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  2. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    About the going rate for that work.
     
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  3. Andych

    Andych Well-Known Member Premium Member

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    Picked up my Barrel today.. he had even given it a bit of a bead blast for me..
    It is going to stay oily until the weekend when I can give it a good clean in hot soapy water.. rinse several times and then look at assembling..maybe... depending on the temperature :)
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  4. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Nice. Make sure you pluck that O ring out to clean out any grit.
     
  5. Andych

    Andych Well-Known Member Premium Member

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    I actually got out into the Garage and did a bit over yesterday and today (Weekend).
    I used my JB Weld to fill some gouges in the clutch cover and also fill some detail where the kick start would be on the TT350 donor.
    As is always the case... fill sand.. clean, fill some more, sand etc. The only real issue is JB Weld takes a while to harden and when it does... it is certainly hard...lol
    I still have a couple of areas to tidy up with some more fine sanding / filing and re-priming, then I can paint it to look like Aluminium again...lol

    I also grit blasted the centre stand and side stand and then put a light coat of Kill Rust Black Gloss onto them. I will try and get another coat on tomorrow afternoon and leave them hanging up until next weekend.

    I had a good look at the springs for the Centre stand and Side stand as well as the bolts... both are really average and as I need a couple of other small items I will probably order them from IMPEX. That way I know they are right.

    I also used my Dremel to open out the holes for the exhaust pipes on the 350 head to match the 42mm diameter of the SRX600 pipes I have. They still need a little cleaning up but the pipes fit nicely with a little clearance for expansion rates when hot :)

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  6. Andych

    Andych Well-Known Member Premium Member

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    I also did a very quick check of my ring end gaps and I am pretty sure they need filing.. not much though.
    According to the specs that came with the piston and rings I need to multiply my piston diameter (in inches) by .0050 to get the end gap.
    My piston is 87mm so that is 3.425 x .005 = .017 (17 Thousands of an inch). I checked with my feeler gauges and the .017 wouldnt go in.. .014 was the largest I could fit.
    I dont have a super fine thin file so when I take my head back to my machinist I think I will have him gap the rings and fit them to the piston. By the time I buy a Piston ring expander and ring file I may as well let an expert do it...
    Some things I am better off letting someone else do... even if I can do it.
     
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  7. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Old rule of thumb was .003" per inch of bore diameter, which would give .010" end gap.
    I would go with the .014".
     
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  8. Andych

    Andych Well-Known Member Premium Member

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    Hmmm there is a chart that is with the rings and there are a number of different dimensions to use dependant on the intended use... I think I picked standard road use which was .005 per inch. I need to have another look I guess.
    I just dont want to run the risk of seizing it for the sake of 3 thou :)
     
  9. Andych

    Andych Well-Known Member Premium Member

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    The chart from Wiseco is shown below... I will get myself some new feeler gauges as these ones are 20 odd years old and a few of them are not as smooth as they should be...including the .017 and .014.
    Wiseco are really fussy with the way they want the rings ground too.. I must admit.. I have only ever used a super fine small file.. almost like a nail file but a proper tool.

    I had a really good look at the head yesterday after giving it a really good clean.. and it turns out there is a crack and when I started measuring the new camshafts and looking at the journals in the head I have decided that this head is basically toast.. I dont believe the journals can be cleaned up and the clearance then would be out of spec.. so it just isnt worth spending any more time on it... I have sourced another head which looks to be in really good condition.. no cracks and it has original Valves in good condition. Hopefully they will lap in nicely and I wont need to spend $$ on having them ground. That will offset the cost of the new head to some extent.
     

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  10. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    The top end of this engine has been giving you a bit of a hard time Andy. Will be good to see it together.
     
  11. Andych

    Andych Well-Known Member Premium Member

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    Yep... but that is what happens when you start modifying away from standard I guess... Possibly would have been better off just buying a 350TT engine.. although no electric start and gearing is all wrong...lol
    Still hasnt deterred me.... I want this to be a real little sleeper.. :)
     
  12. 2valve

    2valve Well-Known Member Premium Member Contributing Member

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    I agree Andy , it will be a super nice sleeper that's for sure. The SRX will also be sleeping in my garage, look forward to that ;).
     
  13. Andych

    Andych Well-Known Member Premium Member

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    Found the appropriate return springs and bolts for the centre stand and side stand.. just looking at how this cenetre stand retracts I can see why there wasnt one on the 3WP... it hits the lower shock mount on the dogleg... I might have to sort out a stop once it is all sitting how it should.
    Fitted up the stands... and the back rim (loosely as it is far from finished) and sat it up... might give me a bit of motivation to see it sitting there like that.
    I also took the chance to pop the belly pan on just to see how my SRX600 exhaust pipes fit in (roughly) and what sort of room there is underneath for my exhaust... the answer is... not a lot.. by the time there is a merge connector in there it will be tight to get an 1.75" pipe out the side... I might have to mock up my cactus cylinder head in the correct position so I can get a better idea... hmmm I dont really want to wait till I have the engine in to fabricate what I need.
    Lets see how I go over the next few weeks with all the other stuff.
    I finally charged up my good compact Panasonic camera which makes it far easier to take pics and post them than the phone..

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  14. Andych

    Andych Well-Known Member Premium Member

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    With a new (old) TT350 head arriving as well as a new High performance cam chain it shouldn’t be too long until the engine can be fully reassembled.
    I bought some engine paint the other day. Duplicolor new cast aluminium.
    It is as close as can be to factory finish apparently.

    I am very tempted to get the bottom end all assembled and painted. Let it dry and then install the into the frame.
    It is lighter and less chance of scratching the engine or the frame although there will be plenty of protective cover (bubble wrap) around the frame etc.
    Although I could just as easily assemble the lot as it is only a singe pot thumper

    I also need to get into the calipers. Get the pistons out and see what they are like. Hopefully they are not pitted and I can just paint them and assemble with new seals. They are pretty grotty but it looks to be mostly fork oil. When i took the hoses off nice clear brake fluid came out which is a good sign.


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  15. Andych

    Andych Well-Known Member Premium Member

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    This was from last weekend trying to get an idea of how my engine pipes will run.

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    And some of the parts that arrived, new Centre and kick stand springs and bolts among them.

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  16. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Will you be able to get the head and barrel on with the bottom end in the frame?
     
  17. Andych

    Andych Well-Known Member Premium Member

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    That is the $68K question... Barrel, yes, thats easy but then the head might be difficult to get under the frame bars.. doing the cam timing etc is easy enough with it all in the bike... Maybe i will just build it all and find someone to assist me lifting it in..
    thanks for asking the difficult questions @Murdo :)
     
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  18. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I reckon the barrel and head might fit with the engine in the frame ?
    pic from perth street bike's

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  19. Andych

    Andych Well-Known Member Premium Member

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    Having had a look through some other pics it should be fairly easy but then I need to be super careful painting everything separately as well... here is another pic...
    That pic from Perth Street bikes is the SRX that my Machinist built...it won a prize at Throttle Roll a ew years ago and gave me the info I needed to use the FZR front end etc.

    SRX Bare.jpg Now that is a very rough bike...lol
     
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  20. Andych

    Andych Well-Known Member Premium Member

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    So... managed to get home from my Moree trip a little earlier than I thought.. thankfully. I broke the return trip into a 4.5hr yesterday and 5 hrs today.. much better than 9.5 hrs in one hit..
    When I got here there were a few goodies waiting for me..
    My Top engine mount bracket from Japan as well as an SRX250 3WP Japanese Service manual. I will need to use Google Translate to get the parts I want into English... mainly the wiring diagram as they are slightly different.. (I do have a 3WP harness).
    There was also some of that lovely split self wrap braided cable sleeving.. for the 3WP Harness :) and I also bought one of those Leak-down testers.. not sure if the adapters suit my various cylinder heads but I am sure I can sort that out.

    I dont think I will get to do anything this weekend.. We are off to Melbourne tomorrow to see Michael Macintyre (pommy comedian) at the Tennis Centre and then some retail therapy for the Boss.. (not with my money thankfully :) ) which only leaves Sunday.. but the lawns need mowing etc etc..
     
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