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GSXR250R (GJ73A) Race Bike Build

Discussion in 'Suzuki 250cc In-line 4's' started by Boydie77, Apr 22, 2014.

  1. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Just take out a second mortgage.
     
  2. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  4. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    @Boydie77
    I would be thinking about a set of Carrillo rods or at least crack test, polish and shot-peen the standard rods.
    They will be the first thing to break in a race engine.
     
  5. Grasshopper

    Grasshopper Well-Known Member Dirty Wheel Club

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    Awesome! I'll start saving my bikkies.... wait, I paid less for my bike....
     
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  6. Boydie77

    Boydie77 Well-Known Member

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    Yes, with import GST and broker fees the FCR's came in at $1750AUD, 3.5 times the purchase price of the bike LOL

    Yes Malstrom my plan is to get both the crank and rods polished and balanced (I'll do the polishing myself). I'm curious now to get a quote for some Carrillo rods but I have a feeling they may out of my budget. I have to draw the line somewhere..! :(

    Good news is I got the yellow bike going today, I think the previous owner had so much trouble getting it started because the plug leads for 3 & 4 were around the wrong way! Makes me worried about the bike shop who did the rebuild on it now, I hope it wasn't them who put the leads on like that... I did run it with my rebuilt set of carbs which probably helped, the ones on it don't look good. The classic silicon smears around the float bowl plus the cable purch is cracked and held together with wire. The leakdown readings (ie compression) are good but it has a noticeable rattle from the top end. The cam chain tensioner looks different from my other engines, it might be from another model bike. I have a spare one so will fit this and hopefully the noise will go away. Valve clearences will need checking too of course. I really hope I can transplant this engine into the race bike while the fast engine is being built.

    I also forgot to mention that my Over Racing exhaust arrived from Japan, I've only had a chance to take a quick look at it so far. Unfortunately its a street system and not full race spec, hopefully it delivers some HP because it looks very cool. It's pretty grubby and rusted between the center downpipes but should clean up OK, will post some pics when it's presentable enough :)
     
  7. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Aaaagh and ouch! Suddenly all the money that I have spent on my project seems small. You are committed now Boydie, all in!
    I would have found some way to go via an intermediary with a much lower declared value.

    Once upon a time in Aus, when I imported some Mahle pistons, I received an invoice from a shipping agent for an astronomical sum of money for them to clear said pistons from customs. I promptly phoned them up and told them that I did not appoint them to represent me so they could take their invoice and you know the rest. Then I marched into the customs office and asked for the appropriate forms and documents necessary to collect MY goods. As is my right as a citizen. Finally after being annoyed by me for three hours and with no end in sight, one of the helpful officers completed the forms for me (took about 3 minutes). I paid the due amount and collected my goods.
     
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  8. Murdo

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

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    Boydie, the standard rods in most engines are usually pretty good if prepared properly. It is often the rod bolts that are the problem.
    When I raced Ford Escorts with the 1600cc crossflow engine, I always used high tensile socket head cap screws in the conrod bearings. The standard Ford bolt was rated to 60,000 psi, the cap screws to 120,000psi. The SHCS had a slightly taller head (to fit the Allen Key) and I had to be careful to 'clearance' the sump with a hammer. Using these SHCS with polished, balanced,closed and honed rods I regulary reved these engines to 3,000rpm more than they were designed for without ever having a problem with crank or rods (cam followers were the biggest problem at 9,000rpm) on the standard cast crank.
    If you can get a rod bolt out and measure the thread and length, take to a place that sells engineering bolts and see if you can get a match. Make sure the shank is the same length, even if you have to cut a bit of thread off.
     
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  9. Boydie77

    Boydie77 Well-Known Member

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    Yes, my initial plan was to buy a set of used FCR's off Yahoo Japan Auctions to keep under GST threshold but after getting outbid on 2 sets I ran out of patience. Now that I know more about em I'm very glad to have new ones, they are so complex and need proper maintenance, not to mention guessing the spacing, it would have been a real gamble going used. Paying $250 in import fees was a bit of a bitter pill but I didn't see much option with them coming from Webike, at least I got free shipping!

    Thanks for the advise Murdo, I have never attempted anything this big rebuilding engines before, I've only ever put em back together standard following the manuals, so tips like this are great :)

    Rather than veg out in front of the TV last night I went out to the shed for a couple hours to take all the dirt and corrosion off the exhaust silencer. I used 800, 1200 then 2000 wet & dry to get it smooth, then lots of Autosol to bring up the shine. While it's not a perfect mirror finish I'm pretty happy with the result for a hand polish...
    WP_001924.jpg

    I think this exhaust is going to be too special to risk on the race bike! It will look really good on the black road bike tho... decisions decisions!
     
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  10. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    Looking at a set of RS Smoothbores for my bike at $600-700 a pair and I was crying. Holy moly!
     
  11. uber pikey

    uber pikey Member

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    Did you find out if you can fit a 150 rear tyre?
     
  12. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    How's it all going matey..just hooked up back to the thread..god i'm hooked! Just in the middle of another rebuild myself..rods (as standard) are safe to 20K rpm minimum..maybe more..and never had to touch them..send me the bill if they prove otherwise!! For longevity I can see the logic though and may well be a wise idea..the valve trains not the best :) but far from bad..as rough cast as it is those ports are pretty good for a standard production bike..but the dremmel will concur good results! As regards the top end, I've had better results with older valves and more heat cycles..not sure how it works but the older the more tempered..just from experience and not sure on the scientific knowledge behind it but within spec the older the better in this case..some valves come from the factory 'soft' in my opinion but that's just me lol! Just caught the message on timing so will come back to you once I've got the specifics..the race cdi is part number 32900-06C00-1 and comes with 4 different capacitor resistance blocks to plug into the extra slot on the rear of the cdi..most important is to set it up right after you've drilled and slotted the sprockets (any dial guage will pretty much do so long as its accurate)..timing at standard then advancing/retarding to suit based on what your looking for..more than anything its useable power and torque maybe with a bias towards mid and top end your side..envious of your parts supply bud..those bikes look grrrrrrrr...ok..read mmm..and envious!!!!! Keep the updates coming boss..fcr's for the bandit 250 pretty much slot straight on if you get the adaptor plates with it..same carbs with less machining..Christ I wish I lived in aus or you in blighty..I could do with yus now..measuring bores trying to save a set of barrels..49.03 honed with a bit of pitting, 49.05 and were close, 49.07 means i'll let you know tmoz! Service limit is I think about 49.1..but compression suffers after..markedly! If I can ask a question to you with all the knowledge you've gained..piston bore /clearance..0.09 optimum against a service limit of 0.11-0.12..fresh pistons and rings..if not back to webike..the barrels are at nearly £400..advice needed!!!

    Take care mate and catch up soon,

    Si
     
  13. Boydie77

    Boydie77 Well-Known Member

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    G'day Si, only just saw your post I missed it somehow sorry! Unfortunately there hasn't been a whole lot of progress made here in the last couple months, it's been a real struggle to spend much time in the workshop :(

    Regarding bore clearance, I have been working off the Across manual which only lists the service limit clearance at 49.09. Good news is my cylinders getting bored to .5mm oversize have cleaned up perfectly so I now have all the parts needed to build the motor :) These have been done to .05 (I will check & match to the pistons before assembly). The cylinders from my Across engine are in good condition it turns out and measured to be mostly around .05 clearence. My telescopic gauges are just cheapies from eBay, but I took lots of measurements to be sure as possible.

    On the subject of engines, I've leakdown tested both my new arrivals now. The one that runs came back fine with decent figures on all cylinders, but going to check the valve clearances first thing I notice is the cam caps have been put on in the wrong order! For those that don't know the camshaft tunnels are precision line bored and this stuffs that up where really precision tolerances are called for. Thankfully the damage was only minimal but it took a lot of work to carefully sand & polish the surfaces, I think it's going to be OK but I will have to take the cams out again & inspect after the first run to be sure. It's so frustrating to find shoddy work like this, something I really wasn't expecting from an engine that's been rebuilt by a bike shop. GGRRRRRR :( Oh well, at least looking at the bank of FCRs sitting on the motor cheered me up when it was all back together...
    WP_001967.jpg


    The black bike's engine as suspected has some serious intake valve leakage out of cylinders 3 & 4. The leakage past the rings was fairly ordinary on #1 to with it just in the green zone. So looks like a total top end overhaul on this one. I'm thinking it might be a good candidate to get on the road next summer to test some Chinese valves and rings, maybe even pistons. That is a fair way down the priority list though...

    In other progress achieved I have (mostly) made this awesome engine stand! I haven't got much welding experience but my best mate is a master welder and lent me some gear for the weekend and this was the result. I had never used an auto flash sensing welding shield and it's a whole new world! Wow makes it so much easier, now I want to get my own gear and make cool stuff, I already want to make my own tube frame for something now... lol :prankster:
    WP_001972.jpg WP_001973.jpg

    Oh and I have also started turning the stock tail section into a pattern piece to make a fibreglass race tail. I'll get some pictures of that up once it's a bit further along. With a bit of luck I should have the bike back up and running with this new engine for my last track day before the winter break in a couple weeks. Fingers crossed...
     
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  14. Boydie77

    Boydie77 Well-Known Member

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    Hey all, just a quick update. I have managed to swap my one good engine into the bike and after tonight its mostly back together again! This engine is an Across bottom end with GSXR head, there are some small differences I noticed, main one being the gear shaft is shorter and needs the cut down across cover to work. Gear change is rubbing on the frame a bit too but works OK for now. Did an oil and filter change and after a bit of an effort cranking the first time it's starting and running really well. It now likes the choke, idles low smoothly and revs really cleanly. A massive improvement on the old engine already, plus I swear it sounds better than ever too! Hopefully I'll be taking it to Symmons Plains Raceway for the first time this Sunday if the weather is OK. Might be a few of us on 4cyl 250s going up if all goes according to plan, stay tuned for hopefully action report! :)
     
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  15. kiffsta

    kiffsta Senior Member

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    nice mate, loving the thumbs up :thumb_ups:
     
  16. Boydie77

    Boydie77 Well-Known Member

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    OK guys and gals, well it's been longer than planned for the action report but I'm back with good and bad news. The bad is that shortly after making my last post, I went off to bed.... then woke up about 4am in the cold sweats which turned out the be the dreaded MAN FLU!!!! :(

    I was crook as all weekend thru to Wednesday, so my Symmons Plains trip didn't happen. Luckily we had the final ride day before winter at Baskerville today, and good news is I was back to (almost) full fitness and the bike was as ready to roll. It was a really chilly start but with no wind and the sun shining all day it hit the max temp of 12 degrees and turned out about as good as you hope for a Tasmanian winter's day really.

    After my test run last week I expected the bike would start pretty easily, but it wasn't the case. It took a jump starter and HEAPS of cranking to get her to go, needed the choke in the end which is good, but for the rest of the day it ran on the button each time so it's still an improvement I guess but seriously why do these bikes have to be soooo hard to start cold :( Hopefully some Dynatek high performance coils will help, I've bitten the bullet and ordered a set so we will find out...

    First shakedown run revealed it was pulling well off the turns but was down on top end power, I was hitting 15k then just stuttering and stalling out. I had fitted a cheap ebay air filter designed for a Bandit 250 and it has a smaller diameter inlet, plus with the extra resistance of the filter I was pretty sure it was struggling for air. Stupid me had forgot to make a spares list and forgot to bring the old intake flange so I had to make one at the track using a cut off tube of sikaflex, plastic oil container and s**tload of gaffa tape! But turns out it worked perfectly, with the missing top end power restored I was able to go about mercilessly thrashing the little beast around for some great sessions! Early on I got to test out the straight line speed against a ZXR250 and they were neck and neck :) Highlight of the day was going up against my main rival Ian on his well prepared MC22 Honda. His bike still has a fraction more speed but it is really close now. We even did a bike swap and that was a real eye opener. The Honda did almost everything better than mine and was just so easy to ride. It was a bit flatter in the midrange but with a wide spread of power up high it could be kept on the boil for rapid progress. In comparison my bike can pull through a lower gear in a couple spots and get better drive, over the whole lap it's really close. The suspension on the CBR was excellent (Wilbers shock and fork cartridges), with the same tyres it felt may more compliant than mine but also gave really good feedback. Overall I still prefer my stiffer set up but the shock really is over sprung or the shock may need a re-valve. I also need to ditch my ancient brake pads for some with more bite.

    The two things we both agreed on was that the more spacious ergos on the GSXR were nicer for us 6 footers and it also turned in better. The CBR is still an awesome bike in this regard and I had heaps of faith in the front, but with the same faith on my bike its just incredible how tight the lines are you can hold on it. It took until the last session for me to fully let loose and push it to the limit but the bike just felt amazingly planted, almost uncrashable!

    So the day was completed with success, the bike going better than ever but still needs development. I should also mention the gearbox and clutch were much smoother in this engine which was nice. Hopefully it won't have to do too much more work and I will have the race spec engine built for next season come spring, but just have to see how I go. So many jobs to do...!

    I'd also like to send out a huge thank you to @maelstrom for becoming one of my sponsors and providing me with a set of Litetek titanium suspension arms. These were a perfect fit and save 150grams compared to the steel ones. It might not sound like much, but every little bit helps as they say and I will need every gram saved if this bike is to be competitive at the the national level. They are obviously very strong too as the bumpy Baskerville surface and my stiff-as shock & 90kgs is about the toughest test a 250 can give em!
     
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  17. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    All progress is good progress and you found out lots of things that can make the handling & braking, and therefore the lap times, better. The FCR's will give a significant increase in power and can run with a free flowing airbox. Keep it coming
    cheers
    Blair
     
  18. Boydie77

    Boydie77 Well-Known Member

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    A bit more progress made this week, I've got my carbs mounted ok now, using an old innner tube as a sleeve over the inlet to make them fit the stock intake rubbers. They still aren't a fantastic fit, they need to be a bit tighter still but two layers of inner tube won't slide in properly. I'll try and find something a bit thicker and if that doesn't work, some beefier hose clamps to squeeze the rubber down tighter.
    WP_002009.jpg WP_002013.jpg
    I tried these throttle cables but they don't clear the underside of the tank. The cable purch is in the wrong spot, there is no other option but a different cable bracket. Keihin make a number of different brackets it turns out so will order the one I need.
    WP_002011.jpg
    With the tank on, I was able to look under and see what my airbox options are. It's looking very difficult to make it how I wanted with a forward facing air intake. There just isn't enough room under the tank or a suitable clear path over the engine to make it work without serious mods. Also the bellmouths only clear the tank by a few mm further complicating things. At this stage I think the only option will be to make something based off the stock airbox but wider at the top and split horizontally so it can clamp around the intake funnels. Not gunna be easy...

    At least the race bellypan has gone a little better, popped it out of the mould last night.
    WP_002014.jpg
    came up really well, a little rough still in places but trimmed down to shape, sanded and painted it should look great.
     
  19. Murdo

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

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    Could you lift the tank a little to clear the bellmouths and cables?
    Inner tube will swell with petrol.
     
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  20. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Ahh yes, what the good Doctor said is spot on again. That completely skipped my mind. From memory inner tubes are usually made from Butyl. Totally unacceptable with gasoline. Might dissolve into your engine.
     

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