Bike sounds different – Gt125r 2012
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Bike Model = : Gt125r 2012
- Just finished putting my rear cylinder back together timing seems spot on compression hasn’t changed yet I have a completely different sounding bike could anyone help me or has anyone had a similar sounding issue?
- Its firing on both cylinders both exhausts are hot
- Bright blue/white spark
- Carbs cleaned and both cylinders receiving fuel
- I can run the bike on one cylinder either front or back
- It just has a burbly sound to it not the raspyness it originally had
Thank you for taking your time reading my post😃
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Does it ride well ? And does the sound change as revs go up or down ? Does the sound change if the clutch is pulled in?
If unsure, upload a video to youtube –> set it as “unlisted” , it means no one on youtube will search for it.
Copy the share link and post it here, if helps
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Hi Marcel here is a video to try help fix this issue
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Have you gone out with it yet ?
From basically 5 second clips, i can’t tell much as i am hearing the exhaust more than the engine itself, so i will take a shot in the dark to say “it seems OK?” – Have a ride with it first and feel its behavior.
Also if you can feel heavy thumping on the cylinder heads (like someone is banging the door and you can feel it) , you will sense if the crank and pistons are OK ,but use your judgement and do it when its warming up so you don’t burn your hands when it’s too hot to touch.
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Hi Marcel thanks for getting back to me
Had a ride out today did 4 miles if that bike died would randomly fire but not run pushed it home it then decided to fire up again while running it still has the flat sound to it most it would do is 50-60mph also struggled to rev past 11k rpm’s did a compression test bike near the limit on the rear bank but the bike has been like that for a while (125psi when warm throttle open) yet it ran spot on when I first got it compression hasn’t changed i looked over the bike valves sealed fine piston rings where snug at 0.25mm on my feeler gauge put it back together and ever since I’ve had this running issue and a flat single cylinder sounding vtwin
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if intake clearances are 0.10mm to 0.20mm and exhaust is 0.20 to 0.30mm = then valves should be OK?
Would you be able to tell if valves are leaking oil through their seals or did it smoke at any point ?
Take a look at this thread as it’s similar to yours in regards to rebuilds
Valve clearance, camshaft, camshaft tensioner – a problem or a serious fault?
Come back to your topic and let us know
125 PSI on both cylinders when its hot, did you chuck a tiny bit of oil in there (just a little) = Did it go up or down ? (piston rings or valve seals?)
Though… if re-installing pistons back in , it is possible the rings moved out of fashion
Normally rings are staggered like this:
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=========___===The _dips__ you see are the gaps in the rings, if they all line up exactly , that can cause further issues. I can’t remember the exact format off my head (have to read the manuals all over again) but check the 125 manual GV125 from this forum or even manualsLIB website for the cartoon drawings of the pistons to see how the rings get lined up. I had to do this last time as the old engine was eating oil (a stupid Yamaha it was!) , thankfully it hasn’t been too hard to do on a Hyosung bike. Just can’t mess with the vtwin-timings!!!!
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Front cylinder is 150 psi i did the old fashioned way of checking leaky valves put some fuel on the valves let it sit for 30ish mins check to see if any fuel leaked past from what I seen no fuel got past I typically line my ring opposite from eachother did this on other 125’s like the older suzuki dr honda cg and honda xr never seemed to run into a issue no oil is getting burnt as plugs are a nice tan colour no black plugs but also seems to be lacking on throttle response healthy spark timing on rear bank is 2 (ex) facing ⬆️ exactly where the rocker cover bolts go so is the (in) 3 if that makes sense just to get timing out the way to make sure its spot on I’ll get it taken apart tomorrow to inspect that top end again maybe I got unlucky and a valve has now started to leak after first fire up
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