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Post by 1601pete on Oct 1, 2019 22:47:42 GMT 1
Here’s a challenge. List all the possible reasons why a standard 500LC engine with Lomas pipes jetted somewhere handy won’t rev past 5500 / 6000 rpm. I’ve tried everything I can think of. Be interested to see what others come up with without prompting
TIA
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Post by markhoopy on Oct 1, 2019 22:58:08 GMT 1
I'm going to suggest high speed windings but only because someone *always* says high speed windings when bikes won't rev above 5000.
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Post by 1601pete on Oct 1, 2019 23:01:32 GMT 1
I'm going to suggest high speed windings but only because someone *always* says high speed windings when bikes won't rev above 5000. Thanks Mark. Stator has been checked and is good |
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Post by donkeychomp on Oct 1, 2019 23:31:35 GMT 1
H/T leads. Plugs. Coils. Carbs maybe jetted perfectly but are your balls clean (lol).
Alex
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Post by 1601pete on Oct 1, 2019 23:35:18 GMT 1
H/T leads. Plugs. Coils. Carbs maybe jetted perfectly but are your balls clean (lol). Alex Thanks Alex Coils changed, HT leads and plugs changed. Carbs stripped and ultrasonically cleaned. BTW. I don’t think I have the balls your referring to in 500 carbs 😂 |
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Post by roach3 on Oct 2, 2019 0:03:52 GMT 1
powervalves setup correctly? ie not opening fully only on the 350 thats about where they start to open
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Post by rich on Oct 2, 2019 0:34:42 GMT 1
Are the Lomas pipes new to the bike and if so did it rev properly before they were fitted?
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Post by Deleted on Oct 2, 2019 6:24:10 GMT 1
Plugs fouled, main jets dropped out, slide stuck shut on 1 cylinder, choke stuck, carbs generally gummed up, water in carbs, rust/debris in fuel tap/carbs, air box/filter blocked, seized and at least 1 cylinder has no compression, reed snapped. incomplete electrical circuit from pickups/ rectifier/coil, flat battery (unlikely) CDI failed (unlikely)
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Post by midlifecrisisrd on Oct 2, 2019 8:03:13 GMT 1
I'd ask when it stops revving what is it running like
Smokey? On how many cylinders? Sputtering? Sounding flat sounding like a machine gun?
Steve
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Post by LC_BOTT on Oct 2, 2019 8:38:50 GMT 1
Fuel taps can be a problem with these too, there was/is a mod to convert it to non vacuum somehow. Don't forget that extra PV wheel frame/bracket thing, can get seized or damaged.
Is it not revving when static, or when being ridden??
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Post by 1601pete on Oct 2, 2019 10:22:59 GMT 1
Gents thanks for your replies / interest
The bike has been owned by a friend for about 8 years. Barely turned a wheel in that time and whether it was running right from
When he owned it is a bit of a mystery.
It’s feel flat when it gets to 5500/6000 rpm. Like it’s lean I guess. Not rich like it’s on choke or like a machine gun as someone described it.
Initially we tried all of the following:
Checked stator
Changed out plugs, leads, coils, loom, powervalve controller, CDI.
Checked powervales, cable around the right way, operation etc.
Ultrasonically cleaned carbs,
Checked jets sizes cleanliness ,Float heights
Checked compression
Exhaust Pipes clear
Air filter all ok
Run with fuel cap off
Run with remote fuel tank by passing tap
Swapped out loom.
All of the above made no difference
Managed to get some some kit to do a leak test and it failed. So thought, right we are onto something. Thought it might have been a fueling issue with not enough of a vacuum to draw fuel in? And or running way to lean.
Changed out cranks seals. Checked reeds etc. Rebuild and now passes leak test. But made no f ing difference.
Last night I’ve taken the carbs off for a millionth time and I’ve set float height right on top end and probably a 1mm over. (More fuel in float bowl).
Will try another run again tonight but it doing my head in!!!
If that fails. Next thing is to swap out carbs from a donor bike. I’m thinking it’s needle / nozzle related.
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Post by LC_BOTT on Oct 2, 2019 12:40:16 GMT 1
If you've had it apart, are the cranks timed/balanced in the correct position? I think they can be done on front or rear crankhaft. If not, I'm assuming there will be lots of vibration too.
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Post by 1601pete on Oct 2, 2019 12:52:11 GMT 1
If you've had it apart, are the cranks timed/balanced in the correct position? I think they can be done on front or rear crankhaft. If not, I'm assuming there will be lots of vibration too. Thanks, yeah cranks / balance shaft all timed up ok |
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Post by tacky1 on Oct 2, 2019 14:44:00 GMT 1
Do you have access to another CDi box and maybe a PV box,
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Post by 1601pete on Oct 2, 2019 15:14:44 GMT 1
Do you have access to another CDi box and maybe a PV box, Thanks Tacky1. Yes tried swapping out with known good☹️. As per my things already tried |
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Post by copper99 on Oct 2, 2019 16:22:41 GMT 1
Mine had similar issues and felt flat, would rev fine in neutral but really struggled out on the road, that was crank seals / piston rings stuck in the lands but as you've changed them and almost everything else its a tough one..
Maybe consider having it on a dyno, see whats going on under load, a good dyno man will be help further diagnose it for sure..
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Post by steve h on Oct 2, 2019 18:30:32 GMT 1
Fuel starvation. Air filter.. bunged up? Oiled? Dyno.
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Post by beardy on Oct 2, 2019 18:32:53 GMT 1
Throttle cable actually opening slides fully?
Sorry I’m sure you’ve checked that:)
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Post by 1601pete on Oct 2, 2019 18:35:08 GMT 1
Throttle cable actually opening slides fully? Sorry I’m sure you’ve checked that:) Thanks Steve, yeah...checked that 👍 |
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Post by 1601pete on Oct 2, 2019 18:36:19 GMT 1
Update,
Gone to far on the float height. Bottom cylinder(s) flooding now. 🤬
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Post by muttsnuts on Oct 2, 2019 18:51:31 GMT 1
you fitted the pistons in the correct cylinders?, the front and rear pistins are different, if they are fitted incorrectly you will suffer this, the front cylindera are crank case induction, the rear cylinders are reed valve induction, the pistons are different and dead easy to get wron, also the heads are different front to rear, so check them as well. Also PV's not fully opening or set up incorrectly or the PV levers are fitted on the wrong PV's, they are marked up "1" and "2", also check that the PV cables are set correctly and that the pulley is free to move when the cables are disconnected. Check for thePV's being seized, front cylinders are prone to it, especially after being stood a long time, if they aren't opening, then you will struggle to get past 6k rpm, also check that the PV's are fitted in correctly (not 180 deg out) as otherwise you are buggered and its barrels off to fix.
Other than that, the exhausts are either knackered, bunged up, or just plain wrong
HTH
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Post by Deleted on Oct 2, 2019 18:53:19 GMT 1
It might sound a bit drastic but disconnect the pipes. If they are blocked (some people have left rags and stuff in there by accident) that would def stop it revving. It will be fkin loud for the 3 seconds you will need to run it to prove the point
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Post by 1601pete on Oct 2, 2019 18:57:20 GMT 1
It might sound a bit drastic but disconnect the pipes. If they are blocked (some people have left rags and stuff in there by accident) that would def stop it revving. It will be fkin loud for the 3 seconds you will need to run it to prove the point Thanks. Defo no rags anywhere. It’s been completely apart |
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Post by 1601pete on Oct 2, 2019 19:01:10 GMT 1
you fitted the pistons in the correct cylinders?, the front and rear pistins are different, if they are fitted incorrectly you will suffer this, the front cylindera are crank case induction, the rear cylinders are reed valve induction, the pistons are different and dead easy to get wron, also the heads are different front to rear, so check them as well. Also PV's not fully opening or set up incorrectly or the PV levers are fitted on the wrong PV's, they are marked up "1" and "2", also check that the PV cables are set correctly and that the pulley is free to move when the cables are disconnected. Check for thePV's being seized, front cylinders are prone to it, especially after being stood a long time, if they aren't opening, then you will struggle to get past 6k rpm, also check that the PV's are fitted in correctly (not 180 deg out) as otherwise you are buggered and its barrels off to fix. Other than that, the exhausts are either knackered, bunged up, or just plain wrong HTH Thanks Dave. Powervalves definitely all good from every aspect you suggest. In addition pretty sure heads are in right as they are different. Rear head has a recess for thermostat housing. Interesting point about pistons. Appreciate OEM pistons are different front to back (windows etc). This doesn’t have OEM pistons but aftermarket. When I took it apart I kept the pistons with the cylinders. Not aware that after market pistons are different front to back? Although I appreciate that Mitaka do windowed rear pistons now Exhausts are defo the right ones and clear Video of it ticking over flic.kr/p/2hpbN9w |
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Post by marrcel on Oct 2, 2019 19:07:52 GMT 1
Fuel cap? Breather clogged?
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Post by hoist1 on Oct 2, 2019 19:09:35 GMT 1
It might sound a bit drastic but disconnect the pipes. If they are blocked (some people have left rags and stuff in there by accident) that would def stop it revving. It will be fkin loud for the 3 seconds you will need to run it to prove the point I knew someone that fitted a new exhaust to something (a 4 into 1)that then wouldn’t start, it had waste metal obstructing it inside during manufacture. |
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Post by hoist1 on Oct 2, 2019 19:11:30 GMT 1
Can the throttle slides on a 500 get mixed up?
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Post by 1601pete on Oct 2, 2019 19:12:18 GMT 1
Fuel cap? Breather clogged? Thanks Marccel. Tried with fuel cap off and also by passed fuel tap by trying a separate remote tank |
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Post by 1601pete on Oct 2, 2019 19:13:14 GMT 1
Can the throttle slides on a 500 get mixed up? Not 100% sure. I will investigate. But revs fine not under load |
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Post by muttsnuts on Oct 2, 2019 19:34:35 GMT 1
do the PV's cycle when you switch it on, if so, which way do they go?, also, have you had your finger up the exhaust ports to check the PV's are fully open when they are meant to, don't just do one, do all of them as I've had one where the PV just in one cylinder wasn't moving and it turned out that it had sheared in the middle due to being seized
Also, do the PV's start to move at around 6+k when revved, as the PV controller might be knackered or even the servo itself, which is highly possible as it is located near the rear wheel and if the rubber boot is missing/perished then it gets covered in crap and seizes up really easily
One thing you can do, is take the PV cables off, get 2 8mm bolts 65mm long, slot them through the PV clamp fork and into the 8mm holes in the barrels which are used for alignment of the PVs, this will pin the PV's open for each bank of cylinders, that way you can eliminate the PV's from the equation when you test it - clearly stuff like this is way easier to do on a dyno than running it up and down the road
HTH
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