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I hate MOT time! I think it's because I do all my own servicing and maintenance work so the MOT is like someone else judging my ability to look after the bikes.
 

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Discussion Starter #42
right!! it's like exam time isn't it... dammit ;)

Also historically I've never had more vehicle failures than right after an MOT so a vehicle going straight through makes me *extremely* nervous
 

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Discussion Starter #43 (Edited)
ok so I think we actually figured out what went wrong and why. Thanks to my friend TamiyaCowboy from the scooter forums (where I have my super-stretched fatty neos build thread - which is here for anyone who's interested in mental stretched scoots : https://www.scootershack.co.uk/threads/yamaha-neos-50cc-build.37580/page-10 ).

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no? ok then..


so this is the teardown video which was more just seeing *what* had happened, rather than necessarily figuring out *why*. I was hoping to prompt conversation to figure out *why* it happened and I think we figured it (full convo is in the youtube comments).


So it goes a little something like this...

it looks like when I did the clutch change, I incorrectly re-fitted the oil strainer. I thought it was just *an* oil strainer, and hadn't realised that the main oil pickup is right above the sump plug, so it's very much *THE* oil strainer. I put it in the wrong way up which meant it got squashed flat against the surface above.. which can be seen here (pic from the spare motor):

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As you can hopefully see the strainer should sit like a little cup over the oil pickup hole, and that ensures that even if it's blocked a bit on one or more sides, there's still plenty of surface area for oil to get through.

Me, not realising that it was the *MAIN OIL STRAINER FOR THE MOTOR AND ACTUALLY A VITAL COMPONENT*, somehow put it in upside down and it got squashed flat against the surface above. I'd been looking for the oil pickup but was expecting a sort of nozzle on a stick like which points into the sump, like you'd see on a car motor. Big mistake.

So picture the little brass mesh instead of being a nice little cup shape with a cylindrical straining area, gets squished flat as if trodden on. It still sealed against the oil pickup hole (more or less) so the motor seemed to be fine - i'd been running with it that way for months and clearly it was ok since I'd been doing wheelie practice and generally wringing its neck as I normally would, but the actual straining area was much reduced.

When there's a serious problem it's normally more than one thing going wrong at once and this case is no different. Whilst the motor was kinda ok with the squashed strainer, then when I put it in the wrong gear, the timing chain was suddenly under a lot of load and did a good job of shredding the cam chain guides, which introduced a bunch of plastic shavings into the oil.

Even the that would probably have been ok, had the oil strainer not been squished flat. With it being flat the effective "straining" area was reduced to the tiny amount of mesh which covered the oil pickup hole (literally jsut the size of the hole which is like 6mm) and as soon as a bit of plastic blocked that it was oil starvation and game over. All the rest looks to be knock-ons from that - no oil, piston rings scoring the bore, subsequent heat-discoloration of the little-end from blow-by etc. etc.


In the video where the engine died I would bet a fiver that's the "floop" sound we heard partway thru (something blocking the pickup), and possibly the momentary power loss around the 9 min mark (
).

It's only on conversation where TamiyaCowboy was outlining what he thought had happened that it prompted me realising the thing about the strainer, and at the time I still didn't know that was THE strainer for THE oil pickup, not just something cosmetic to try and catch bits in the oil. In the teardown video you can just see me remove the strainer which was squished flat but I didn't realise the relevance at the time.


So there we go - annoying because it's clearly doubly my fault, having first fitted the strainer wrong and then messed up with the gears - either one on its own probably wouldn't have been the end of the world but together.. yikes.

I've added a note on my clutch change video to make sure to put the strainer back in the right way, with a link to a diagram which shows it installed correctly..so hopefully anyone else watching the video doesn't make the same mistake.


Fortunately I had a spare engine there so I could pop the clutch cover off and have a peek inside and underneath which is what convinced me that's what happened.

I don't *think* any plastic shavings got up inside the oil pump but it looks like you can't remove it without removing some fairly hefty gears on the clutch side, which is beyond the scope of this repair. So on the last oil change I squirted some WD40 up the oil pickup hole to see if I could rinse out any loose bits which might have got past the strainer but it seemed clear. There were never any plastic shavings on the intake side of the oil filter so I guess I have to assume that the strainer was still doing its job, albeit a little too well at the end.

Figuring this out actually gave me some peace of mind since not knowing why it had happened wasn't helping my post-failure anxiety. It looked like oil starvation, sure, but why? well know I know, and all the rest fits with knock-ons from that.


I had been wondering whether the manual timing chain tensioner had contributed to the failure - for example when I put it in the wrong gear I thought perhaps an automatic tensioner would have had some "give" where the manual one has none.. but actually checking the mechanisms of both type of automatic tensioners, they also don't have any give (08-13 is a screw drive, and 14+ has a ratchet) so actually I think the tensioner made no difference.

I didn't know that when I put the engine back together so I went with an automatic late model tensioner. Originally I'd been wanting to use a late model tensioner anyway but at the time I wasn't happy that the ratchet was engaging properly, hence I went with the manual one. But having learnt what I've learnt I don't think the outcome would have been any different with an automatic tensioner... so now she ticks a bit. However I did also want to absolutely rule out any tensioning errors so I think the late model automatic one was still the right call for the moment.

knowing what I know now I'll probably switch back to a manual on the other motor since I loved it not ticking and the bike seemed really happy until I forgot how gears work.



The 180cc kit is now in, and seems happy enough. I've not changed anything else so it's still stock injector, stock cam, same baffle arrangement in the exhaust etc (even though i have a high lift cam and 10-hole injector sat here)... I just wanted to change as few things as possible to get me back up and running. I want to A/B test the cam and injector so will do that on the other motor once i've got the engine dyno set up.

We're currently approaching the 50miles mark on the new motor. I've done a couple of oil changes and this last one there was almost no plastic bits (vs a few more the time before) so it looks like perhaps what I'm doing is working.

Once I get over the 100 miles mark I should be able to relax a little. It's currently still on the stock 14:48 but with all the extra torque i'm forever running out of gears, but even so she tops out at 45mph in 6th at around 5krpm (I'm keeping her under 5k except for passing that occasionally to accelerate).


Having learnt where the oil pickup is (in the most expensive way possible) I'm a little concerned re doing wheelies since it's quite forward...and although the case design should mean it doesn't run dry it's something I'm gonna look into a bit more before I go nuts doing endless wheelies. Fortunately that's not really a problem atm since I can't keep it up there but I'm hoping it'll become a problem eventually.


For general peace of mind (rather than for wheelies, but also a bit for that) I'm considering adding an oil pressure switch/sensor to the hole in the head where you check for oil flow. It's only a tiny little m6 bolt so is going to be a bit tricky but I think turning a little adapter for a vw golf pressure sensor which screws into that hole should work. That, along with a big Fkoff buzzer/LED should at least give me a heads-up if there's a sudden pressure loss.. at least while she's on probation and till trust is re-established. it's not much but if i'd known there was a problem I could have stopped and those few previous seconds might have meant I didn't melt the engine.

Really there should be no need for the oil pressure sensor but understandably I'm super twitchy about that at the moment ;)

On the motor I'm building up I might expand the thread of that little oil check hole so that the golf sensor fits directly, but that's not something I want to get into with the engine on the bike.


Currently the fuelling is just my old "best" map with +50% fuel added across the board and that seems to work ok - but it will need fine tuning. That was actually the easiest bit - once I fired it up again it ran on the old map but was rough as anything. Came inside - tweaked the map and uploaded to the PCV and then she purred. It's probably a tad rich at the moment (I've got +40% on the other map slot and seemed less happy) but rather that than too lean I guess.

I've got myself a wideband o2 sensor from LDperformance which should let me dial in the mix properly. I'm a little concerned that the injector is running +70% duty in places on the map so long term the bigger injector is probably a better option but till I can get live feedback on the AFR mix that seems like too much of a gamble.

WidebandKit2.png


I've not been able to source a replacement centre section for my exhaust (to weld in the o2 bung) so I guess I'm gonna have to do it on my current one and just don't mess it up ;)


Amazingly enough when you take away the anxiety and stress about the situation and the crappy timing, the bits I ordered and didn't need.... the actual upgrade was literally just the cost of the 180cc cylinder (£~85) and a bunch of oil and filters, and a couple of bolts. If you're not starting from a broken engine full of shredded cam chain guides would actually not be so bad to do. Having some way of adjusting the fuelling is an absolute must though, it was not happy on the old map, which was itself pretty rich, and even the "B" map (which was same plus 10%) wasn't enough.... though it looks like we might have a way to do that using injectors with higher flow (vs stock).. which may mean you don't need a PCV or similar...


I'm aiming to start work on the spare motor right away and see if i can get it back up and running as bone stock, and then tune the absolute sh!t out of that using the engine dyno to find the best combo of parts. That would eliminate the guesswork and hopefully along the way I can test out some common mods (e.g. egr delete, airbox mods, exhaust combos) and perhaps we'll then be able to say for definite what works and what doesn't... Ideally it'll go from stock -> tweaked 125, then 180cc kit on speeduino management (arduino-based ECU) with all the works (cam, injector, bigger valves, porting), ultimately perhaps a small turbo or supercharger...just because it would be mental and to prove to myself I can do it ;) (though that's likely to be a way off yet).... watch this space!
 

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Discussion Starter #45
first longer trip done, nearly at the 100 mile mark, so far so good. Got another trip mid week which should put another couple of hundred miles on....

15t front sprocket only gives me an extra 5mph or so at 5k but it's something..still keep running out of gears ;D
 

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Discussion Starter #46
210 miles down - nearly thru the first half of the break-in miles. So far all still running peachy, didn't miss a beat on that trip, even *fully* loaded up with overnight stuff, work stuff + laptop, clothes, big chain, bike cover, spare oil, tools, the whole shebang. If we can keep this up I think I'll be very happy with her indeed :)

Even dull stuff worked well - like the gps tracker unit I built fits nicely in it's sneaky cubby-hole, the alarm etc was all good, even the tomtom mount and charging bits worked great. I can't believe I got everything to fit on the bars - normally on stunt bikes they tend to relocate or just completely ditch the indicator/lights controls when adding the rear handbrake but somehow I got it all to fit, as well as the map switch, and it actually works in practice \o/.

I'd feel happy trekking considerable distances on this loadout. It's so comfortable but you can still get down when needed. 2 hrs flew by, no shoulder/neck/back pain, just lots of endorphins from the scenery and being on the road. Trip to the south coast and maybe on to lands-end next I think which should take care of the rest of the break-in miles and then some. My friend who I did the other motox bar top yoke conversion for had it fitted and then promptly did 1500km on it (!) also with similar findings re riding position.

The change in my position from the bars, and the slightly geometry adjustment, as well as all the other changes mean I've sorta had to re-learn how to ride, where to put my weight, how much turn-in to expect etc to get a good line, so I'm using the break-in miles to methodically train muscle memory and get my lines and movements to be as smooth and well executed as possible. I thought the break in miles would be painful but they've actually been surprisingly pleasant and most productive.

Still no lower plastics on as I'm keeping a very close eye on the fluids etc and I only have a finite amount of zipties ;)

Pic is in deepest countryside somewhere near melton mowbray

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Discussion Starter #47
so I just did another 2hrs each way trip in the freezing cold to look at another bike which now means we're through the first half of break in miles - engine seems to have loosened up a bit now, feels really rather nice. I allowed myself to have a little fun on the country lanes on the way back and I was grinning ear to ear by the time I got home :D

According to the manual I'm allowed to rev up to 8k rpm now but will still be staying well below that for the most part till we're thru the break in miles. I'd rather be a bit more cautious than risk seizing.

Hopefully another oil change at the weekend, let's see what that brings forth.
 

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8k revs sounds like you have a lot of scope bit in truth the small engine size and single cylinder means you have to use the revs to make significant progress. Hats off to you for keeping siblings 8000rpm.
 

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Discussion Starter #49 (Edited)
yeah keeping it under 6 for that long has been teeeedious :hmm: at least under 8 means i might be able to go 60mph or so, so won't be a rolling roadblock anymore ;)

Tbh on the 180 cylinder that side of it hasn't been a problem in the slightest, even on the 15t front sprocket.

On my recent overnight trip it pulled uphill, fully loaded with panniers (laptop, work gear, overnight gear, drinks+food) and a tailbag (spare oil, massive chain & cover) from 5k. Ok it wasn't *tearing* up the hill but it accelerated no problem and once it got to 6k it was picking up speed even quicker. I'm pretty sure before it would have just laughed and gone a big fat nope, and that would have been on the 14t too.
 

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Discussion Starter #50
w00p! I got my adjusted V5 back from the DVLA, now reg'd as 180cc... all the paperwork fully legit now as far as I can tell \o/
 

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Discussion Starter #52
er, I think it was about £50 extra (around £520 total i think) - I already had the PCV, exhaust system etc declared tho so it was already up a bit over standard. Tbh they are still kinda robbing me since insuring a stock SV650 would be way faster and cost about half what I'm paying but hey I like the bike so it is what it is. Tinkerers gonna tinker.

I probably could have shopped around and got it cheaper but bikesure were the only place who would insure me last year (after the twats at goskippy bailed) so I was happy to let them have this one and I just wanted it resolved without hassle. Next year I'll have a bit more NCB and perhaps be in a better position to negotiate.. till then ¯\_(ツ)_/¯

I learnt my lesson tho - new bike won't need any engine mods, half the weight with more power and should cost peanuts to insure in comparison muhaha :D
 

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Discussion Starter #54
pretty sure I am about your age lol. I've been driving 25 years so cars-wise I can insure what i like, tho i just did my DAS in june so that's probably a factor. I can insure a stock SV650 for about £200 fully comp with no NCB but for some reason my small cc bike moderately tuned is expensive... go figure. Next year I'll be able to shop around a bit more and I would imagine that'll make a fair bit of difference.
 

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Discussion Starter #55
just come back through town and remembered I can turn the little handle all the way and it goes quicker. I've been running in so long I'd forgotten it does that.

So far I've been quite pleased with the 180cc's performance but as it turns out I'd never been in the power band. Doh! Now I have and that's hella fun :D :D

Just spent the rest of the trip back blatting it a bit and laughing out loud like a proper loon. You could probably see my grin from space :D

Still wasn't redlining it since that's not allowed yet, am still in the latter stages of break-in, but I'm allowed little blasts and holy sh!t that's fun. This is on the 15t front sprocket too. The fuelling isn't properly dialled in yet, exhaust isn't de-baffled yet and also doesn't have the cam or bigger injector so there's potentially still a fair bit more to come. Sounds very nice too. SO FUN! moar of this plzzz
 

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Well you've picked the right time of the year to be exploring the engine potential and getting used to the additional power.

I bet it's the same excited feeling you had when you very first rode the R125.
 

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Discussion Starter #57
yeah very much so... thus far I'm very happy indeed with the bike's progress :)

with a bit of luck and once i've got the fuelling dialled in I reckon she should easily have the extra 10mph or so needed to keep up with regular traffic, and not be slower than I was in the car on longer trips, which would be about perfect.

I haven't ruled out an R6 or a 636 in future but I've still got a fair bit of learning to do before I'm ready for that. For me, right now, with my skill level, available funds and requirements...it's spot on.
 

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Discussion Starter #59
I think I'd need to try them out first but I'm in no hurry whatsoever :)

I'd also need to figure out what I'd actually want it for...e.g. just going fast or wheelies etc since that would affect the decision and atm I have no idea.
 

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I think I'd need to try them out first but I'm in no hurry whatsoever :)

I'd also need to figure out what I'd actually want it for...e.g. just going fast or wheelies etc since that would affect the decision and atm I have no idea.
I've never known anyone who is as focused on wheelies as you are.......have you thought about joining the circus? Or a stunt team??
 
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