So Close!...
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@SpookDog Surface area of a circle is pi (3.142 approx.) x (radius squared). Radius = diameter/2 so for a 28mm carb (14 x 14 = 196), x 3.142 = 615.75 square mm. If you have a barrel that's had loads of rebores you can also accurately calculate its cc (or swept volume) using this method, then multiplying by the stroke.
Surface area of the reeds when fully open is a little more tricky as the fully open reed petal produces an opening consisting of a rectangular part (at the very end of the petal) and a triangular part (along both sides).
I guess you could take care of the rectangular part by multiplying opening width x 6.8mm x number of petals.
There's also a triangular part to calculate which would (roughly) be 6.8mm x length of the part of the reed petal which actually opens. Then you'd have to divide it by 2 because it's the area of a triangle, or just leave it as it is and treat that figure as the total surface area of the triangular part per reed petal (because there's one of these down each side). Still not exact because the reed stops are curved so I'd iamgine the reed petals would follow their contour when fully open but it would give you an idea.
I think though that your fitting reed stops which are close to the specified height will improve the way the bike runs; opening up reed stops is one of those things people experiment with in their youth to try and make 125s faster (don't ask how I know lol). Rather like the previous owner of mine who fitted a massive main jet, then set the float height too low so it was trying to suck on a fire hose with a half empty float bowl
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@SpookDog I really don't think an o ring will solve your problems. Your problem almost certainly lies within the cooling system. Sticking/seized thermostat, defective water pump or defective pressure cap. You can easily eliminate the water pump by removing the hose and check if it's pumping and the thermostat by removing it and put in a pan of water on the hob and check the water temperature when you see it open.
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@SpookDog memo
Head gasket fitted. Radiator maintaining coolant at correct level. Temp good @ 140miles...
Poor Symptoms: still stumbling, misfires, knocking @ throttle just cracked open/idle cruising speed...
Find cause,
To check: exhaust manifold & spring seal. Coil. Flywheel side seal. -
Anyone used hi temp rtv silicon to seal a spring mounted exhaust?...
Rem: 210 miles, temp still good, especially for ambient temp. Coolant level still at filler neck bottom...
Still missing/stumbling (popping & knocking) quite badly @ low revs...
Checked airscrew, also carb & inlet for air leaks: all good...
Checking stator side seal before swapping out coil & CDI & source coil, pickup, & sidestand kill switch solenoids (2 of) & other ignition electrickery ...
P.S. Will try swapping out exhaust if necessary...
Edit:
Bodge sealed the rotor side seal with silicon and a smear of grease, also silicon sealed the side cover to make it as airtight as possible: running a lot better at low coasting/cruising speed without knocking/missing. Longer trip needed to be sure, definitely suspect the seal is leaking air. Would of expected oil leakage tho’... -
Tested the bike with bodged seal: what a difference! No popping, knocking & missing at all! Good smooth resolution of revs all through the lower end like I’ve never had!..
I never thought about the seal before cause it was replaced new with the bearings when I first built it. Teach me to buy fleabay seals
Will do the hole and self tapper screw trick and replace with a good used original I have a few of now...
P.S. Copper RTV silicon seems to work very well on the spring mount manifold!...
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Removed and replaced the seal. Took 20 mins. Didn’t need to make any holes, just popped it out (carefully not to scrape the crank) with a small flat head screwdriver. Other drifted in easy with a smear of grease...
Will be test riding bike later...
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Still popping & knocking a bit, but on a much narrower margin, and then only when hot...
Not the result I was hoping for. It is a lot better, but not 100% The change was so profound I was almost certain it was the culprit...
The copper rtv silicon is holding up really well on the exhaust manifold though
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I’m @ 535 miles with no head problems. Radiator is full, cooling is perfect...
Copper rtv still doing fine on manifold...
Swapped coil out with no difference. Bike still popping & knocking bad when it gets hot. I’m still thinking that it’s an airleak somewhere on the block. I don’t think it’s the pilot jet because it’s fine when cold, which would be when the mixture needs to be rich enough (& is!) Waiting on a new genuine seal (flywheel side) from PJME. Got a new genuine clutch side already to go. I’m not gonna take chances on pattern parts again if possible...
I can’t find any signs of 2T leakage on the crank casings join. I did wonder because I used red hematite instead of silicum sealant on the join...
Airscrew is very responsive for the first time ever. Will check the pilot jet again, but am convinced it’s not the problem. Is the same with different carb...
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@SpookDog said in So Close!...:
These things are made to be ridden! I just wish that the saddle didn’t slope down & forwards so much, because anything over 30 miles and it gives my poor old ass a right work over!
Calum, did you ever sell your original RE forks?...
Glad to see someone else say this
I’m 6ft and I always find one my bollocks getting squished and my ass going dead on long rides I’m always sliding right forward on the banana seat, I love it but I wouldn’t mind something flatter like the WR200.
My sperm count would probably appreciate too -
Bud! I call it ‘dirt ball’
it’s a fucking nightmare. It’s on the list to reupholster a new seat. I brought a spare especially. It’s just not a priority atm. You can get silicon seat pads, but I haven’t spotted a good fit yet...I’m 5,11 and can’t fold my legs up anymore and still work the gears...
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Re cleaned the carb out last night, paying special attention to the pilot jet. Also I sealed up the hole in the bottom of the casings as well as the seam/join with silicon RTV sealant.
Took the bike out for a 70 mile ride and it has been very good! Really good ‘resolution’ throughout the Rev range, especially the ‘throttle just cracked’ problem area. I’m not sure if it’s the sealant that has fixed this or the carb. All I know is that I’ve cleaned the carb a lot of times with no results. Even on the jetting I’m on now...
Looks like a bottom end airleak was causing problems since day one.🥴 ...Only thing is it’s taken over 600 miles (of knocking & misfires)to figure this out, and the head gasket has been failing at about 700 miles before! Whatever tho! As long as I fix this eventually I don’t care anymore
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744 miles and still running. Bike is running @ 95%+ still. Descaling the .25 pilot jet that came with the 2nd carb seems to of done the trick, there was a lot of hard deposit inside that wasn’t obvious to (my) naked eye until it was gone. Still think there’s an airleak (small) when hot (bottom end. Not top). That or the mixture screw wants tuning...
Well happy with results for now. Just worried that 600+ miles of missing &knocking have already taken the toll on the head gasket.
Right fork seal fixed...
Edit: I forgot to memo that I stripped & cleaned carb when I bodge tested the rotor side seal. The pilot jet definitely seems to of been the biggest culprit. Can’t believe how long it’s taken to suss out
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@SpookDog really mate sealing up the hole under the engine won't help anything.as for your carb, have you removed and cleaned the emulsion tube? There's so much more to cleaning a carb than the jets. What part of the country are you in? Someone on this forum may be able to help you out.
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I sealed up the whole underside seam, including the hole. What I know is a casting feature but still has area inside that has access to the crankcase seam. I’m a fool but I’m not that stupid. If you’ve read this thread you’ll see I’ve tried everything to suss this problem and I’m basically crossing t’s & dotting i’s for any possible cause...
Yeah I removed and cleaned the emulsion tube as well as making sure the plastic breather pipe and air access to it was unimpeded...
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@SpookDog I just thought that if it was leaking then you'd surely see evidence of fuel/oil leaking or be able to feel the air by running your hand over it? I have been keeping up with this entire thread and I understand you're trying to eliminate everything. Obviously something somewhere that you're missing and the most annoying part of it, it's probably a stupid little £10 part and 20 minutes work. These type of problems are surely the most frustrating of all.
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Sorry bud, I’ve been pulling my hair out for over a year, I do get really frustrated with it sometimes. It’d be a lot easier if it had been running properly at the start, but I haven’t been able to get it properly 100%, Close sometimes, but no cigar
worst thing is I’m usually pretty good at fault diagnosis. Believe it or not! -
@880 miles. Slightly worried cause the radiator level has been down slightly the last couple checks, only 5mm but it’s how it starts. And about the right mileage...
Still running the same, slight ‘splurble’ at coasting with throttle just cracked. None of the knocking & lurching misfires like before though...
Looking like it was a too small pilot jet causing a lean spot misfire has been my problem all along...
Can’t believe my luck that I couldn’t find a genuine Mikuni .25 jet for sale outside of the USA! Or that the one in my second (immaculately clean carb I brought recently) carb would be half blocked with hard deposits that I couldn’t see without a magnifying glass! OMFD’s! You have to try and laugh!
