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Post by geoffers997 on Sept 26, 2020 17:02:07 GMT 1
Hello All, My 1983 31K is giving me the run around, its an unrestored but immaculately maintained bike with only 9000km on it. The engine hasn't been split but its been maintained with Teutonic standards of attention.
What is foxing me is this:
It fires first kick, idles, revs to 6000rpm and progresses to 6000rpm all as I'd expect. That is the good bit
Here are the issues (forgive the ignorance here - when I say left I mean the side with the choke on):
Get to 6000rpm and it bogs down, hesitates and makes short jerks and make some 'pfffft' noises from I think the right cylinder.
It doesn't want to rev past 7000rpm on the road under load but will rev easily past that sat in the garage
The right hand exhaust comes up to temperature, the left gets warm but not hot
The right hand plug is a nice light earth brown colour, the left is black and wet
The left exhaust is wet at its tail end - the right is dry
Riding the bike it isn't smoky and up to 6000rpm rides fine, click it down a couple and it just doesn't want to know.
This is what I've done:
Done a search and followed advice people have given to similar issues:
Replaced the plugs and air filter
Cleaned the right hand carb - it was immaculate in any event
Checked all the carb settings and dropped the needle one notch on the left carb only.
Checked the oil pump - it looks very new and is in spec
All to no avail.
The bit I find weird is no matter where I put the air screw on the left carb, it makes no difference.
I've not got my multi-tester with me just now so can't check the output off the CDI etc
Thanks in advance!
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Post by shaunthe2nd on Sept 26, 2020 17:08:59 GMT 1
Strip and clean both carbs including removing the brass balls and cleaning the air correction circuit. Plenty of details on here how to do it if you do a search. Lots of other possibilities but this is quite a common problem and an easy fix so worth doing.
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Post by Shytalk on Sept 26, 2020 17:09:00 GMT 1
Most people will advise to do a leak test, 9000km isn’t much but the engine - if it hasn’t been apart, is over 35 years old
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Post by midlifecrisisrd on Sept 26, 2020 17:52:50 GMT 1
2 things
Clean behind your balls 😁
It's the air correction circuit
Leak down test, crank seals are 37 years old now.
As it goes to 6k I don't think cdi but check the pv's start to open at 6k ish, fully open by 9500 (sounds cruel revving it that high in neutral but a few seconds won't hurt)
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Post by marrcel on Sept 26, 2020 18:34:26 GMT 1
Cdi suck after 35+years
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Post by copper99 on Sept 26, 2020 19:47:16 GMT 1
It fires first kick, idles, revs to 6000rpm and progresses to 6000rpm all as I'd expect. That is the good bit It doesn't want to rev past 7000rpm on the road under load but will rev easily past that sat in the garage Thats exactly what my RD500 did...Was the crank seals in the end. Started and ran easily, revved up fine in neutral but wouldnt rev out under load, in use. Low mileage isnt always a good thing...
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Post by geoffers997 on Sept 27, 2020 8:56:06 GMT 1
Thanks for all your advice - top notch.
So, plan of action: 1. Ordered up some 4.5mm brass balls 2. Whip both carbs off and then decide how brave I'm feeling - I don't have a pillar drill so may farm this out to a local engineering company just up the road 3. Clean behind where the balls sit. 4. Reassemble and test 5. If still no good, then pressure test.
I was initially thinking if there is an air leak then it'll run lean not rich but if its leaking into the gearbox then it'll draw oil from there making the plug look black, wet and oily.
Depending on the result of the pressure test, I'll proceed from there; maybe need to split the cases and renew seals - I'll do this at some point anyway, just didn't want to do it right now.
I'll post a separate question on pressure testing.
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Post by shaunthe2nd on Sept 27, 2020 10:00:10 GMT 1
The balls are easy to drill as made of brass. Centre pop the top, then I use a small drill, 2mm or less with a hand battery drill. Take your time and drill half way through the ball. Take drill bit out of drill and insert shank end into the hole you have drilled. Then gently move it left right up down to break the seal of the ball which allows you to prise it out. If doesn't work first time drill a bit further into the ball and try again.
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Post by geoffers997 on Oct 11, 2020 18:30:00 GMT 1
Update on the mystery:
1. Drilled out brass balls and as expected, everything was clean as a whistle. 2. Rebuilt both carbs paying attention to needles and jets - all are standard sizes, checked float height - spot on. 3. Rough and ready I know but I checked for a suck on the oil filler - nothing, oil level in engine hasn't moved and the oil pump is spot on too. 4. Test ride: sh1t, no change, still fluffing at about 6k and won't rev past about 7k 5. Took end cap off power valve cables - they're correctly adjusted and cycle about 1/4 to 1/3 of a turn when the ignition is switched on 6. Revved it to full throttle in the garage, the PV stuttered a bit but didn't really move, I could hear electrical sounding snaps and pops in the exhaust note. 7. Consulted Haynes manual - I need to check the servo, PV controller and CDI.
The Haynes manual has test values for the PV controller but none for the CDI although I do recall seeing CDI test values on the forum, I'll go look for those.
My questions please:
Are there any other tests or values I can check with my multi-tester ?
If the any of the three units are fooked, what are the options: Does anyone refurb them; is it NOS or 2nd hand or are there alternates that are a better bet (I recall seeing discussion about alternative CDI units on the forum)
Thanks all
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tomtom1
Thrash Merchant
Leeds
Posts: 355
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Post by tomtom1 on Oct 11, 2020 20:02:59 GMT 1
Hi are your power valves 180deg out?, if you look between your cylinders at the front you can see the joiner that links both power valves together, the head of the bolts should be facing up toward the underside of the fuel tank. if the head of the bolts are facing down toward the ground, the you need to just unbolt the power valve pully spin power valve, and refit pully.
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Post by chrisg on Oct 12, 2020 17:21:18 GMT 1
Did this issue just happen or have you been doing and work/repairs?
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Post by geoffers997 on Oct 12, 2020 17:36:49 GMT 1
Its been there since I got the bike, I've improved it a bit by doing all the things I've talked about on this thread.
I'm thinking its electrical now rather than fuel / seals.
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tomtom1
Thrash Merchant
Leeds
Posts: 355
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Post by tomtom1 on Oct 13, 2020 21:55:23 GMT 1
Hi are your power valves 180deg out?, if you look between your cylinders at the front you can see the joiner that links both power valves together, the head of the bolts should be facing up toward the underside of the fuel tank. if the head of the bolts are facing down toward the ground, the you need to just unbolt the power valve pully spin power valve, and refit pully. have you tried this?
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tomtom1
Thrash Merchant
Leeds
Posts: 355
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Post by tomtom1 on Oct 13, 2020 21:55:33 GMT 1
Hi are your power valves 180deg out?, if you look between your cylinders at the front you can see the joiner that links both power valves together, the head of the bolts should be facing up toward the underside of the fuel tank. if the head of the bolts are facing down toward the ground, the you need to just unbolt the power valve pully spin power valve, and refit pully. have you tried this?
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Post by speedar on Oct 14, 2020 17:14:18 GMT 1
Had a similar problem recently with my TDR. Kept going onto left cylinder only and burning out plugs in right! Found that needle in the right carb wasnt secured properly to slide due to rounded screws. Was running way too rich on right carb! Replaced screws so that needle secured properly to slide. Job done! Also worth checking PV position as mentioned in previous posts.
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Post by geoffers997 on Oct 26, 2020 10:14:23 GMT 1
Hi All, Update: - Powervalves checked - all correct and opening at just over 6000rpm
- Carbs cleaned and set to within an inch of their lives (balls included)
- Oil pump checked
- New plugs and caps
- Wiring checked
- Pressure tested ok
Still wont rev past 7000 under load and hesitates and jerks while attempting to get past 7k
Left hand plug wet and a bit oily. Right hand plug looks normal
Please can I ask for for thoughts on my next plan:
I reckon its an ignition problem so:
Replace coil with Banshees - Norbos look good
Beg a loaner CDI and do a substitution test
Beg a loaner stator and do a substitution test
If its the coil, then fair go, the Banshees will be the fix
If its CDI then I guess I'll need a Zeel or similar
Stator - I'll get it rewound
Thanks all
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Post by huggy76 on Oct 26, 2020 19:21:17 GMT 1
Have you tried pulling the choke on when it starts to struggle and splutter to see what it does?
When you have cleaned the carbs did you remove the emulsion tubes from the carbs to check they where clean?
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tomtom1
Thrash Merchant
Leeds
Posts: 355
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Post by tomtom1 on Oct 30, 2020 20:47:15 GMT 1
Hi are your power valves 180deg out?, if you look between your cylinders at the front you can see the joiner that links both power valves together, the head of the bolts should be facing up toward the underside of the fuel tank. if the head of the bolts are facing down toward the ground, the you need to just unbolt the power valve pully spin power valve, and refit pully. you say they are opening, but are they 180deg out? easy to check just get on your back look up to the power valve joint between the cylinders, if you can see the 2 bolt heads then they are 108deg out.
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Post by geoffers997 on Nov 8, 2020 18:46:42 GMT 1
Hi All, Update: Check PV were is the correct way up - they were.
Bought myself a fleabay compression tester. Notwithstanding its accuracy, I got 50psi on both cylinders. Nowhere near where it should be in any language or universe.
Fearing the worst, I thought I'd whip the head off and see what carnage was within. Long story short - no carnage, cylinder bores smooth as silk, a little carbon on the exhausts ports and some leakage on the left hand power valve seal plus what looks like a fair amount of blow past on the pistons. I say what looks like as the only screw that I failed with was the second power valve connector joint screw so I can't lift the barrels and take some measurements / photos until I can extract it.
So, next plan: If the pistons which are 9000km old originals on zero oversize are good then I'm thinking new rings (likely from PJME as I think the ones they sell will fit) and a hone of the barrels to make sure they get a good bite.
Do I buy a honing tool and DIY (ball type or the three stones type?) or take the barrels for a pro job?
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Post by midlifecrisisrd on Nov 8, 2020 19:00:18 GMT 1
If going to hone them get it done professionally
At 9000 km I'd hope you wouldn't need to but you may see ring marks where it has been "parked" for so long
I take it you did the compression test with the throttle wide open?
If so I'm expecting one of 2 things
The rings are gummed up with old 1980's oil sludge or the last owner is a liar and its done more than 9k
Steve
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Post by geoffers997 on Nov 16, 2020 21:26:37 GMT 1
Barrels off - pistons look ok - see pic . A very very small amount of coke on the crown and a bit of evidence of blow past - nothing a scotchbrite pad won’t clean up. The rings seem worn according to the spec in the Haynes manual so the plan remains to hone the barrels and put new rings in. Now here’s the interesting bit: big signs of the power valve seals leaking and on stripping, the valves are proper gummed up.
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m
Newbe
Posts: 1
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Post by m on Nov 25, 2020 21:34:57 GMT 1
My 2 pence:
1) The link piece between the powervalves wears meaning that the lh valve does not turn the rh - remove the rh cover and check. This would dull the performance but it should still rev past 6000. 2) A worn ignition switch can fail to send power to the pv servo even though the engine runs fine otherwise. This stunts performance above 6000 but you wouldn't expect it on a low mileage bike. 3) Check the rh exhaust for mouse nests/food caches. It's not common but if it's happened no amount of carb stripping will fix it. You've got the exhausts off now, it's easy enough to bang them on the ground.
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Post by loudy on Dec 9, 2020 21:44:20 GMT 1
Have you had any luck with this mystery?
Was the link pipe between the carbs fitted - not the balance pipe betwixt the inlet rubbers, the choke link pipe?
Just a thought!!
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Post by loudy on Dec 9, 2020 21:51:31 GMT 1
And, does your fuel tap operate as it should - with the vacuum pipe connected as it should be?
Just another thought!!!
Good luck!
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Post by bare on Dec 9, 2020 22:18:15 GMT 1
As above Check the fuel flow from the Tank Could be restricted due to age / corrosions in the tank?. IF one cyl /plug is clean then the ignition system is Fine , or at least usable. It's a Lost spark setup where Both plugs MUST fire or neither will.
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Post by geoffers997 on Dec 9, 2020 23:16:21 GMT 1
Just a bit of an interim update:
Cylinders are at PJME - they’ve had a look and they’re ok - just need a hone and some new rings.
When I get the cylinders back then it’s new power valve oil seals (they were weeping) and all new gaskets.
I’ve had the carbs and fuel lines apart - all clean as whistles. No rust in the tank.
Once it’s up back together my next area of focus will be the stator and CDI.
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Post by loudy on Dec 9, 2020 23:23:55 GMT 1
Have you had any luck with this mystery? Was the link pipe between the carbs fitted - not the balance pipe betwixt the inlet rubbers, the choke link pipe? Just a thought!! It sounds as if you are in touch with your onions but was the aforementioned pipe fitted? It's omission will upset the situation considerably!!
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Post by geoffers997 on Dec 10, 2020 15:32:53 GMT 1
Yes, link pipe between carbs - the rubber one between the carb bodies is in place.
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Post by LC_BOTT on Dec 10, 2020 15:55:31 GMT 1
I'd be sticking a new set of pistons in too, mine was at a slightly higher mileage (13K) but found some genuine Yamaha stock pistons and rings, so fitted them after a light hone.
Standard ones are a bit easier to find as well, due to the higher number of re-bored cylinders out there.
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Post by geoffers997 on Mar 28, 2021 13:02:03 GMT 1
Hello Forum, Bit of an update - I’ve been busy with work so no been able to spend as much time as I’d like in the garage:
I stripped the top end and got the exhaust cleaned and cerakoted.
Barrels were inspected by PJME and pronounced good. A hone, new rings and little ends plus gaskets and PV seals went into it.
I’ve swapped the coil for a known good one.
Carbs have new mains and jets. They’re clean (balls out clean) and floats triple checked.
It’s cold on the right side hot on the left - swapping plug leads makes no difference.
Runs lumpy, wet plug and won’t rev out.
I can see a spark but reckon it’s just not firing properly on the right side.
Any ideas where to go next?
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