Gsxr250 engine help

[Askor]

Hey guys,
A while ago i bought a gsxr250 (gj72a) in parts to work on as a project.
Iv put it all together and took it for its first test ride today but there is a really bad rattle coming from the timing chain. Also there was a loud-ish ticking from the valve cover, so i killed the engine immediately and let it cool down, tried again and the ticking is gone? I've had a look at the CCT and it seems to be fine so i guess I'll have to put a new timing chain in it..
Also started tuning the carbs aswell under load (hence the test ride)
Any advice? I havent taken the engine apart yet but i have a spare engine that i have, so swapping parts shouldnt be too much of an issue.
Cheers :)

[SILVER SUZI]

Well I'm no mechanic, but I'm pretty sure ballancing the carbs whilst on a test ride is going to be ....um......errr.... somewhat difficult!
I ballanced the carbs on my old GSX when I had one. You need to make sure the diaphrams don't have so much as a needle hole in them or you'll never get them ballanced. Likewise your intake manifold.
Then get hold of a carb ballancing tool (I borrowed one off someone on here), or build one if you are going to keep the bike for a while. It's basically a vacum gague for each cylinder and some vacum tubing.
Then most importantly......................get the fuck onto youtube! and someone will tell you how to do it. You need the right revs, and you need to know which screw to turn where.

[ducatilover]

Check valve clearances
Balance carbs (make a manometer with 2t oil, fuck the vac gauges)
Check then CCT again, when it's out put it under pressure (err...push on it quite hard)
Measure the CCT spring against Suzi specs
Check how tight the chain is by pulling up on it on top of the sprocket

Buy a big as fuck hammer.

[Askor]

Sweet as guys cheers! I didnt mean syncing the carbs whilst riding i meant riding it to see how different adjustments affect the power at different revs..
Thanks for your help I'll keep you posted!

[ducatilover]

Basic rules of thumb, idle to 3krpm = pilot jet and screw. 3k-8k (or 1//3ish throttle) = floats, 8k-3/4 throttle needle taper/height/spring rate, top end = main jet.

Generally.

[Askor]

Ok, so far I've got her tuned nicely and fixed the timing chain rattle by swapping the CCT with a spare i had. But there is a ticking noise coming from the front of the motor around the exhaust manifold. Am i right in thinking that there could be a slight exhaust leak and I just need to fiddle with the seals? Or could there be another problem I should worry about like valve clearances? I have tried getting the valve cover off but it is stuck on and it wont budge. Any advice on this?
Cheers guys

Sorry for all the questions I'm 16 and this is my first project :)

[Scream]

I have a GSX-R 250 also, I originally noticed a rattling noise coming from what seemed to be the timing chain when it was at low RPM, after contacting my mechanic who specializes with older bikes he told me that it was a completely normal thing for these bikes, and that it's nothing to be worried about.

My guess is it's just a compromise to help rev the engine so high seeing as they aren't as packed with all the technology that later bikes have.

[Akzle]

Also started tuning the carbs aswell under load (hence the test ride)
Any advice? I havent taken the engine apart yet but i have a spare engine that i have, so swapping parts shouldnt be too much of an issue.
Cheers :)
swapping parts between worn engines..... hrm. as long as the replacement part is closer to spec than the replaced part shouldn't be much issue. just be wary/ don't asssume it will fix your problem.
CCT spring/slides etc - check are to spec.
also CCT length/wear. is it a triplex-duplex type chain? either way, git 'r off and check for wear. + sprockets.
else i think Mr. GN had a fairly succint summary.



Then get hold of a carb ballancing tool (I borrowed one off someone on here), or build one if you are going to keep the bike for a while. It's basically a vacum gauge for each cylinder and some vacum tubing.
first off i'd start with a bench sync (plus i had to anyway a'cause i didn't have a vacuum gague) pull carbs off bike and lookin up the arse of them make sure your air-pilot/divot/idle hole/bypass bit is 1/3 visible in each carb. lock up your balancing screws.
put back on bike, set to a high idle, run until engine is warm - set idle properly.

then vacuum gauge is good idea because cylinders wear differently and thus draw differently. do with new plugs and clean fuel and warm engine. (and after CCT has been spec'd) then she'll be a vroom vroom.


...Am i right in thinking that there could be a slight exhaust leak and I just need to fiddle with the seals? Or could there be another problem I should worry about like valve clearances? I have tried getting the valve cover off but it is stuck on and it wont budge. Any advice on this?
tap tap taperoo!
with a soft faced mallet. probably has a good dose of old RTV sealant that's gone gluey. just smack the shit out of the sides of the rocker cover (gently. ish) to break the seal. do not try prying it with crowbar/screwdriver as you will fuck it. at best chip cover/block, at worst fold/bend/snap your cover.
when re-fitting, makes sure to tighten cover screws as said in manual. usually to half torque, criss-crossing outward from the middle bolts. then again to torque spec in opposite order.

valve clearances should definitley be checked, and since you have the top off anyway you might as well. you'll need to know the spec but it'd be about .010" intake and .018" exhaust. you'll need to find out which timing marks to line up for your model so the cams are pointing the right way etc.

as far as exhaust seals... is it a flush/flat manifold-with-gasket-type set up, or is it tapered pipe and flange-per-cylinder type set up?
either way, new seals never go a miss.
loosen all muffler bolts, start at the cylinder torquing to spec, then work your way to the arse of the bike tightening teh bolts.

[Askor]

Almost forgot about this thread!
The ticking issue was the exhaust seals - two were installed incorrectly. Once I put them in right the ticking noise was gone. The valves were within spec, and I fixed the timing chain rattle by changing the CCT.
Happy riding!

[Akzle]

Almost forgot about this thread!
The ticking issue was the exhaust seals - two were installed incorrectly. Once I put them in right the ticking noise was gone. The valves were within spec, and I fixed the timing chain rattle by changing the CCT.
Happy riding!

a happy ending.

if only thread could have a happy ending... or, y'know. an ending.

[rok-the-boat]

Balancing carbs - The guages are expensive. In the past I have found that taking off the carbs and just making sure they open at exactly the same time is good enough. The eye is amazingly accurate. Also, I think someone else mentioned it - CV carb diaphrams on olderbikes crap out. They must be soft and flexible with no holes. They can be bloody expensive. If they are 'porous', you will never balance your carbs.

[ducatilover]

Balancing carbs - The guages are expensive. In the past I have found that taking off the carbs and just making sure they open at exactly the same time is good enough. The eye is amazingly accurate.

No it's not.

You need to balance them correctly because different cylinders will have different amounts of vacuum for a given throttle opening, hence the use of a manometer, which is very cheap to build.

Doing it by eye will not achieve much at all

[rok-the-boat]

Oops - yes - I was wrong. I was thinking of normal slide carbs not CV carbs - got muddled. With slides you can get away with doing it by eye - but not CV ones.