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ART-ADS
Renault 5 Driver



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PostPosted: 13:28 - 23 Aug 2018    Post subject: VT125 top end issues Reply with quote

Bike was running fine as I sorted out the cutting out issue by fixing the vacuum being caused in the fuel tank. I take a 100 + mile ride to an event and when I get there my front cylinder is ticking like mad.

I decide rather than get stranded by pulling it apart id take my chances and ride It home, power was down a LOT could only top 50mph, exhaust note was crap and tinny/ ticking sound and both cylinders were ticking

me and my dad had checked the valves on the rear cylinder only 500 miles or less beforehand and they were perfect so we didn't check the front- no ticking sounds just a check as the bike was on 23.5k miles and we didn't know how often it'd been serviced

I take the day off work to go through the heads and adjust the valves- exhaust is meant to be 0.2, on the front it was 0.6 and the back was also way bigger than it should, intake is meant to be 0.15 but again was 0.3 and the other one was much larger than spec

so in the 250 mile round trip my valves had gone from in spec to miles out??? didn't make sense to me

I thought it was the cam chain but nothing was broken and the tensioner worked when I pulled it out to have a look, back together no issues.

I then go to start thee bike and it starts right up! perfect I thought but I take it out for a ride and im down on power, I used to be able to cruise in top gear at 40mph at really low revs so I didn't annoy everyone with the loud exhaust and it sounded better, now I have to rev it a lot to get the same speeds and I didn't even hit 50 on the way to work where I normally do on the short straights (my commute is 5 mins down back roads and town streets)

the exhaust note after the adjustment had gone from the tinny sounding like a valve will drop to the same as normal (at idle until you have to rev it out where it just sounds like its revving high but not comfortable) but theres still a ticking sound coming from the engine (hence why I think its a worn cam) I asked my dad and he said a worn cam was rare??

when it took it out the revs also stuck a bit, like it'd rev high and not move faster (clutch slipping maybe??) then it'd fix itself sort of its difficult to explain that part

please any suggestions put down there i have a 300 mile round trip in the middle of next month and i want it running fine then, on the backroads id like to cruise as it did before at 40-50 at low revs and 60-70 when you're gunning the little thing

if iv made a mistake in what iv done let me know i need to get this sorted out!

thanks!

info (may be useful) - 2003 Honda vt 125 shadow, now on 24K miles, custom exhaust (straight through)
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Evil Hans
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PostPosted: 13:45 - 23 Aug 2018    Post subject: Reply with quote

Did you up-jet or re-tune at all when you fitted the exhaust?

Could be running lean and overheating / burning valves ?
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ART-ADS
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PostPosted: 13:59 - 23 Aug 2018    Post subject: Reply with quote

Evil Hans wrote:
Did you up-jet or re-tune at all when you fitted the exhaust?

Could be running lean and overheating / burning valves ?


definitely a possibility - i checked my plugs when i first ran the bike with the new exhaust and they weren't lookin lean, im planning on taking it to a dynojet tuners so it runs right with it anyway but wanted to get a bug eye filter first but eh probs worth doing beforehand.

thanks very much for the reply i'll action on that, any other ideas please feel free to comment
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Paddy.
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PostPosted: 15:45 - 23 Aug 2018    Post subject: Reply with quote

If you put it back to standard, does it all run fine.
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ART-ADS
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PostPosted: 16:09 - 23 Aug 2018    Post subject: Reply with quote

Paddy. wrote:
If you put it back to standard, does it all run fine.


Rode it for hundreds of miles before issues with it
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WD Forte
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PostPosted: 16:53 - 23 Aug 2018    Post subject: Reply with quote

Dont waste your money
No dyno jet tuner is going to change it from being a 125
Do the tappets, put new plugs in and put the original exhaust back on and hope you haven't burnt a valve out.
I understand you want it to sound 'cool' but baffles aren't there
just to keep the neighbours or the gubment happy.

Your time would be better spent understanding how a 4 stroke engine works ( look up exhaust back pressure) and to to keep the machine in optimal condition
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ART-ADS
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PostPosted: 17:26 - 23 Aug 2018    Post subject: Reply with quote

WD Forte wrote:
Dont waste your money
No dyno jet tuner is going to change it from being a 125
Do the tappets, put new plugs in and put the original exhaust back on and hope you haven't burnt a valve out.
I understand you want it to sound 'cool' but baffles aren't there
just to keep the neighbours or the gubment happy.

Your time would be better spent understanding how a 4 stroke engine works ( look up exhaust back pressure) and to to keep the machine in optimal condition


Will putting a baffle in the one I have now have the same effect? Again not trying to change it from a 125 wanting to fix a problem with it (ticking) and the issues with the reduced power? Dyno would only be to ensure Iím running correct fueling for the bike. Iíll find out what a tappet is and sort that out. Any ideas about the engine ticking??? My mate said camshaft
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Ste
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PostPosted: 17:41 - 23 Aug 2018    Post subject: Reply with quote

Put the original exhaust back on.
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WD Forte
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PostPosted: 17:46 - 23 Aug 2018    Post subject: Reply with quote

Its very hard to diagnose online with scant details
but generally speaking, loose tappets ( valve adjusters) 'tick'
worn camshafts knock
broken or very worn cam chain tensioners and guides can be noisy too.
Exhaust header leaks can cause odd noises too
Y'see? its hard to say for sure, only examination and testing gives
accurate info.

Any baffle is better than no baffle I suppose
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Evil Hans
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PostPosted: 17:47 - 23 Aug 2018    Post subject: Reply with quote

WD Forte wrote:
Your time would be better spent understanding how a 4 stroke engine works ( look up exhaust back pressure)


^ This
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ART-ADS
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PostPosted: 17:57 - 23 Aug 2018    Post subject: Reply with quote

Yep I already am learning about engines, mostly my bike specific but also learning from guys who build bikes for a living that Iím mates with, they all run straight pipes and go thousands of miles no issues ? So idk about that part but itís worth a go.

Iíl Make a video and send a link so you can help further whether itís a knocking or tapping,

The loss of power still hasnít been explained. Or the revs sticking any ideas?

Thanks.
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ThatDippyTwat
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PostPosted: 18:25 - 23 Aug 2018    Post subject: Reply with quote

ART-ADS wrote:
Yep I already am learning about engines, mostly my bike specific but also learning from guys who build bikes for a living that Iím mates with, they all run straight pipes and go thousands of miles no issues ? So idk about that part but itís worth a go.
...
The loss of power still hasnít been explained. Or the revs sticking any ideas?

Thanks.


It has been explained. Back pressure, exhaust scavenging, or more accurately, the lack of.

Bet you your bike they're not riding 125's for thousands of miles with open pipes.
It's far more noticeable on a 125 that, say, a big V-Twin.

If they're teaching you, they're not doing a very good job.
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Ste
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PostPosted: 18:29 - 23 Aug 2018    Post subject: Reply with quote

ThatDippyTwat wrote:
If they're teaching you, they're not doing a very good job.

They're not teaching him, they're taking the piss out of him.
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ThatDippyTwat
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PostPosted: 18:52 - 23 Aug 2018    Post subject: Reply with quote

Ste wrote:
ThatDippyTwat wrote:
If they're teaching you, they're not doing a very good job.

They're not teaching him, they're taking the piss out of him.


That's a bit like shooting fish in a barrel with this kid. He's not so much on the spectrum, as in some sort of zen-like tune with the spectrum.
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stevo as b4
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PostPosted: 19:07 - 23 Aug 2018    Post subject: Reply with quote

If your valve clearances have gone massively out of spec in 300miles, then that's going to be related to your ticking/tapping sound and likely to explain the loss of power. Have you done a compression test on both pots with a hot engine?

You might have to take the heads off and see what's going on with the valves and their seats. As others have said if you've had open pipes on it for a while and not re-jetted the carbs, it's fairly likely you've been running too lean. On an engine that Revs to 11-12k that would worry me.

As to pipes themselves, well other than the lean running condition that's possible, they won't necessarily make the bike run worse than std. There's probably a tiny power gain in there somewhere with the right (std bore size) pipes of the ideal length or a tuned 2-1 if you spent ages setting up the fueling on a dyno. An open air filter might also make a change to the air-flow and fueling, but it would need time spent and a box of jets and experience while the wide band is shoved up each pipe.

The back pressure thing on any four stroke is largely bollocks, but flow velocity is the crucial thing in exhaust system design.

I have nothing against people wanting to tune a 125 as long as they accept it's lots of money for little gain, and that you can't just slap a new part on and expect it to run peachy.

I'd be looking at your valve issue and doing compression checks before messing with jetting though. Good luck getting it sorted.
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WD Forte
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PostPosted: 19:13 - 23 Aug 2018    Post subject: Reply with quote

The loss of power still hasnít been explained. Or the revs sticking any ideas?

Sadly my psychic powers have waned since that Green Kryptonite incident
( Damn you Lex Luthor!)

You supply relevant info with supporting pics and vids and you'll
always get folk chiming in with much better guesses and advice.

Bike builders?
Pfft
Chrome don't get you home!
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ART-ADS
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PostPosted: 11:22 - 08 Nov 2018    Post subject: Reply with quote

update

it was the cams, both worn to absolute shit. battery was old so changed that and it starts on the button better, also cam chain tensioners were old so changed them for manual ones, what else oh yeh the rocker arms were worn to shit changed them out. and still got the straight pipe lol
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BusterGonads
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PostPosted: 19:29 - 08 Nov 2018    Post subject: Reply with quote

ART-ADS wrote:
update

it was the cams, both worn to absolute shit. battery was old so changed that and it starts on the button better, also cam chain tensioners were old so changed them for manual ones, what else oh yeh the rocker arms were worn to shit changed them out. and still got the straight pipe lol


Why did all of this mayhem happen in a few hundred miles? It was running fine (you say) then suddenly it was completely fucked. Why is this?

Put the exhaust back on and return the tuning to standard - if you can. I've seen case after case on a CG125 forum of young lads wrecking their bike's performance to try and look or sound cool by putting some loud exhaust on. They won't listen to advice because they know some 'bike builder' who makes cool bikes, then they arrive back asking why the bike has gone all wrong a few weeks later or even sooner.
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stevo as b4
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PostPosted: 01:19 - 09 Nov 2018    Post subject: Reply with quote

I'd be more worried about why your cams have worn severely and once the hardened surface was damaged what the silvery grinding paste in the oil has done to the rest of the engine bearings etc. Its likely a top end oil feed issue that caused the cams to wear, and on small bikes with low oil capacity I'd say 90% of the time it's due to neglect from running low on oil or not changing it often enough. If your bike doesn't have a full flow replaceable cartridge filter then 1000miles is as far as oil should be taking you between changes.


A straight through exhaust or a standard system won't make jack shit difference to the above issue, though if the straight pipes were causing it to run leaner, (read hotter) then that might have increased oil consumption from std, which if not picked up soon enough would be a good story as to where your oil and cam lobes went.
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Teflon-Mike
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PostPosted: 08:18 - 09 Nov 2018    Post subject: Reply with quote

To be fair, Buster, the cams going, is very likely unrelated to his pigging about with the exhaust. When the follower has worn through the case-hardening ion the cam surface, they will tend to wear at an alarming rate.

Question is how and why did they get that bad.

125's suffer at the hands of learners; they either get completely neglected, or they get killed with kindness, with an awful lot of simple ineptitude chucked in to make matters worse.

VT125 shaddow motor, is also a plumbers nightmare. Same engine in the Very-Oh-Dear-Oh, it's over intricate and convoluted for that Harley-esque look.. which just makes it a nightmare to work on... 'cos not only is it overly intricate and convoluted, its also diddy!

Bought for the 'look'.. owners are to start with more likely to send any time they do on the thing with solvol than a spanner; and any money they have to chuck at it will more likely go on tassled bar grips or western style saddle bags, than on oil or brake pads....

The most likely root case of this things maledies, is a long string of style conciouse, know little owners, who have paid whey over the odds for a 'little' bike, then been loath to spend more on propper maintenance, when a DAS course is on the horizon.

Oil changes, even if contemplated, are likely to have not been done as often as required, or as diligently as they should; tappets will have been left until they are hammering like a pack of pixies on over time in the cobblers shop, cos its so difficult to get at the back ones, and its scary in there... there's OIL! Then WHEN they have finally been tackled... some-one will have struggled to get a feeler guage in there, and worked on the principle that the tighter the better, cos of how rattly they were to start with; tight tappets will load the cam gaces, omited oil-changes will have left hardened steel swarf floating around, accelerated wear will occur.

It wasn't 'sudenly' fcuked, it was fcuked a long time ago... and the fkcedness was just growing, then tipped over the edge.

As Steve sort of suggests though, if its been allowed to get that bad, for so long... and I am sanguine about suggested repairs.... the cams and followers would have been just lip of the lettuce, and chucking money at new cams and followers and stuff, to MY mind, would not be first course of action... its fixing the symptom, not tackling the cause or considering the contributory.

For it to have eaten its own cams... implication is that the thing suffered a heck of a lot of neglect and panic mechanic maintenance.. and failure of the cams, wil have left a lot of unseen damage in the engine, after whatever was responsible for the cams.

Best case... tappets were wound up too tight 'once' motor was run low on oil 'once'.. cams gone... new cams fix symptom, and plenty of flushing should take any residual grinding past out the sump....

But, more likely, its been run low on oil a lot. Its been run with the tappets too tight and too loose for long periods; bearings will have blued, swarf will have got into things like the oil pump, into the galleries, the cylinders will likely have worn as much as the cams, and the thing probably could do with a rebore; small ends will have been ground down by swarf; mains will have been chewed, and big-ends blued.

Whole motor would need a total tear-down to find out just how extensive the damage caused really was, and a diligent rebuild to put it properly to rights...

And likely that still the case.... BUT with a few new bits making good the obviouse, it hopefully wil last a few more thousand... and stacve off being really beyond ecconomical.....

In which time... its dead metal breathing.... it aint gonna get any less dead... so what the heck... chop the 'zorst, fit a screamin'dodo filter, polish the chrome, and make the most of it... whilst it lasts! Lol!
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ART-ADS
Renault 5 Driver



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PostPosted: 10:51 - 14 Nov 2018    Post subject: Reply with quote

Teflon-Mike wrote:
To be fair, Buster, the cams going, is very likely unrelated to his pigging about with the exhaust. When the follower has worn through the case-hardening ion the cam surface, they will tend to wear at an alarming rate.

Question is how and why did they get that bad.

125's suffer at the hands of learners; they either get completely neglected, or they get killed with kindness, with an awful lot of simple ineptitude chucked in to make matters worse.

VT125 shaddow motor, is also a plumbers nightmare. Same engine in the Very-Oh-Dear-Oh, it's over intricate and convoluted for that Harley-esque look.. which just makes it a nightmare to work on... 'cos not only is it overly intricate and convoluted, its also diddy!

Bought for the 'look'.. owners are to start with more likely to send any time they do on the thing with solvol than a spanner; and any money they have to chuck at it will more likely go on tassled bar grips or western style saddle bags, than on oil or brake pads....

The most likely root case of this things maledies, is a long string of style conciouse, know little owners, who have paid whey over the odds for a 'little' bike, then been loath to spend more on propper maintenance, when a DAS course is on the horizon.

Oil changes, even if contemplated, are likely to have not been done as often as required, or as diligently as they should; tappets will have been left until they are hammering like a pack of pixies on over time in the cobblers shop, cos its so difficult to get at the back ones, and its scary in there... there's OIL! Then WHEN they have finally been tackled... some-one will have struggled to get a feeler guage in there, and worked on the principle that the tighter the better, cos of how rattly they were to start with; tight tappets will load the cam gaces, omited oil-changes will have left hardened steel swarf floating around, accelerated wear will occur.

It wasn't 'sudenly' fcuked, it was fcuked a long time ago... and the fkcedness was just growing, then tipped over the edge.

As Steve sort of suggests though, if its been allowed to get that bad, for so long... and I am sanguine about suggested repairs.... the cams and followers would have been just lip of the lettuce, and chucking money at new cams and followers and stuff, to MY mind, would not be first course of action... its fixing the symptom, not tackling the cause or considering the contributory.

For it to have eaten its own cams... implication is that the thing suffered a heck of a lot of neglect and panic mechanic maintenance.. and failure of the cams, wil have left a lot of unseen damage in the engine, after whatever was responsible for the cams.

Best case... tappets were wound up too tight 'once' motor was run low on oil 'once'.. cams gone... new cams fix symptom, and plenty of flushing should take any residual grinding past out the sump....

But, more likely, its been run low on oil a lot. Its been run with the tappets too tight and too loose for long periods; bearings will have blued, swarf will have got into things like the oil pump, into the galleries, the cylinders will likely have worn as much as the cams, and the thing probably could do with a rebore; small ends will have been ground down by swarf; mains will have been chewed, and big-ends blued.

Whole motor would need a total tear-down to find out just how extensive the damage caused really was, and a diligent rebuild to put it properly to rights...

And likely that still the case.... BUT with a few new bits making good the obviouse, it hopefully wil last a few more thousand... and stacve off being really beyond ecconomical.....

In which time... its dead metal breathing.... it aint gonna get any less dead... so what the heck... chop the 'zorst, fit a screamin'dodo filter, polish the chrome, and make the most of it... whilst it lasts! Lol!



hopefully it lasts the next 18 months until I'm 19 Smile
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