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Discussion Starter #1
Am unable to start a TTR225 motor just installed in the Betty Boop TW. Motor has never run for me and came with no pedigree on history or why it was literally in the garbage.
Valves were adjusted when new donor motor was on the bench. They were pretty close to being in spec. Engine turned over nicely on bench test both by hand and by electric starter. Runs through gears nicely, clutch works, plug gets spark, carb seems to be delivering fuel.
Compression was tested with cold motor & throttle held open and observed to be ~ 50psi @ 5,100 ft elevation. Extrapolating correction for elevation indicates this would have read ~80psi at sea level. Still significantly low, right?
Going to re-test now after putting some oil in spark plug hole to see it that identify a ring issue. Am assuming the 50 psi is indicating a real problem.
Opinions?
Suppose I can pull head and look for issues, swap TW head and valve train for TTR head and valves.
But would I be wise to plan on piston and rings too just to be safe?
And as long as I am looking at enhanced jugs for Betty Boop should I not consider not just going from 196 to 223cc, but maybe a full blown 250cc cylinder, piston & head? ( we guys like em bigger:p)
 

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Bent valve stem, or deformed valve stem where it meets the cam, shot rings - could be any of them. The only way to find out is to drop the head and take a look at what's going on. Even if the rings are shot, you're still going to need to go in there after them

IMO, you'd be better off trying to fix the TTR motor than you would boring Betty's out. Very few "big bore" kits match the customers expectations, and a 10% over bore is unlikely to match that with a 10% performance increase

The TTR swap however I can vouch for - more torque and top speed (15 / 45 is standard on the TW225) ....
 

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JTSTDUB's instructions will probably find the problem. But you could also do a cylinder leak-down test. Put the piston at TDC on the compression stroke and pressurize the cylinder. See where the air is escaping. Out the exhaust suspect the exhaust valve. Out the intake suspect that valve.Out the oil fill, rings or piston. Pull the oil filler cap when you do this.
 

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Out the oil fill, rings or piston. Pull the oil filler cap when you do this.
For the benefit of future readers, you'll need to clamp the crankcase breather pipe to detect any excess pressure at the oil filler cap ...... ;)
 

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Discussion Starter #6
At worst case I could get replace the top end with this but re-cycle Betty Boop's 196CC head. [h=3]NEW LISTINGYamaha XT 225 Top End Rebuild Kit Cylinder Piston Refurbished 1992-2004 #99[/h]
Will not the Serow's case accept a XT250 cylinder & piston? I wasn't thinking of boring Betty Boop's engine, it shall sit on a shelf. Instead install compatble parts for the new donor 223cc motor.

Question: Anyone have a link, or info, on how to research a engine's pedigree with just an engine serial number? Wish to confirm correct part compatibility before ordering.
 

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Fred, I am so sorry that you are having problems with this engine :(. Please accept my sincere apologies for sending you down this rabbit hole!

As mentioned already, if low compression is confirmed then the head needs to come off to see if you have valve problems and/or cylinder/piston/ring problems. If the head is okay (fingers crossed!), then that Ebay offer may not be a bad way to go, since a cylinder bore and piston/rings would probably cost you close to that. I would also definitely consider using a Wiseco high compression piston (I can get you the part number of the one that I used when I get home tonight).
 

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Discussion Starter #8
Scholars and gentlemen all!
Nice helpful group to hang out with here. Thanks.

As far as another threads mention of no neutral light I have jumped across the side stand safety interlock grounding that circuit so as to restore starter motor function.
Still no neutral light. While I believe I have good spark measures via a timing light like device is there some other ignition cut-out beyond the starter motor cut-outs? i.e. could I have an undiagnosed ignition error? Spark plug, cdi, stator etc are all from the working Betty Boop chassis.
 

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As far as another threads mention of no neutral light I have jumped across the side stand safety interlock grounding that circuit so as to restore starter motor function.
Still no neutral light.
Fred, I am not an electrical type of guy but can I assume that you have confirmed that the neutral switch in the transplanted TTR engine is functioning and that neutral bulb in the control is not burned out?
 

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Discussion Starter #10
No, 'cause I'm a Neanderthal.
I suppose a test for both would be to jump across neutral light's terminals at connection under seat grounding out the circuit. If switch is bad then neutral light should now come on when bike is in neutral. If starter then can engage when bike is in gear with clutch out then that would indicate a bad bulb in dash.
Any faults in my logic?

EDIT: I did connect the TTR neutral switch to the lead from Betty Boop before buttoning up left side cover. Did not test the switch nor take any special efforts to clean switch's terminal .
 

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I think it's an ignition issue. If you have spark and fuel, you need very little compression to get a motor to start and idle. Might not make much power, but she will start and should start easier than a high compression motor.
With that said, you indicated you got spark. However, you didn't indicate it was timed right. I'd start there. I do not KNOW the TW200 is set up this way, but most motorcycles are; I've sheared the wooddrift key that holds on the flywheel, throwing the timing off as the sensor is now out of time.
Also, I assume you tried a different spark plug? I'd swap it out with known working as well as brand new plug. So many times a plug will spark beautifully when out of the motor, then won't if in the motor under compression. I also will test spark plugs out of the motor but with one still in the motor for the compression. Perhaps there's something going on when under compression that affects the spark as well. So, test plug out of the motor with one still in, then look for spark on the plug out of the motor.
I've got one of those clear things that go in-line to the spark plug that lights up, a neon tube I think, that ionizes the gas when a spark is fired down to the plug.

So spark, fuel and heck, even NO compression will burn. You got nothing trying to start, you've eliminated compression and fuel (I assume with some sort of starter spray fluid), then the spark has got to be missing.

Good luck!

P.S. My suzuki samurai has 80psi warm and it's otherwise bone stock. It starts with only half a click if the timing is right to fire a plug no matte what. I only bump the key. This was my basis for building my TW200; that it's quite possible to get a 4 stroke motor that is mildly tuned to start without having to crank it. My TW now does that as long as it hasn't sat so long the carb fuel is evaporated. Not only is low compression not affecting ease of start, this thing passes California smog with numbers better than new 2018 cars do. My SMOG tech is impressed every time I come in for a SMOG test.
 

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I suppose a test for both would be to jump across neutral light's terminals at connection under seat grounding out the circuit. If switch is bad then neutral light should now come on when bike is in neutral. If starter then can engage when bike is in gear with clutch out then that would indicate a bad bulb in dash.
Any faults in my logic?
Yes - but I'm too tired right now to quite understand (explain) it - but somethings not quite right with that

Suggest we all get some sleep first .......
 

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Fred, when my 2015 started having a running problem I "tried" to do a compression test. I know I did the testing correctly but I could never get the compression to read anywhere near what the manual says it should be as SkiPro3 mentions above. My problem ended up being a bad pulser coil down by the stator. I'm not trying to direct you to that problem just mentioning that it was electrical and nothing to do with compression but I did thoroughly check my valves what felt like a dozen times. Oofta!
 

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If there is a problem with the neutral safety switch (or other safety switch) do our TWs still send spark to the plug? It seems like too much of a coincidence that you have no neutral light. It’s easy to swap the high beam or turn signal bulb in to check if it’s just a bad bulb. Cheers Fred. Hope you get it running soon.
 

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Fred, when my 2015 started having a running problem I "tried" to do a compression test. I know I did the testing correctly but I could never get the compression to read anywhere near what the manual says it should be as SkiPro3 mentions above. My problem ended up being a bad pulser coil down by the stator. I'm not trying to direct you to that problem just mentioning that it was electrical and nothing to do with compression but I did thoroughly check my valves what felt like a dozen times. Oofta!
Kris, did you have a spark?
 

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Discussion Starter #17
With me there is always a chance Joe, thought you knew that.:p

Seriously, I did put the TW left side cover on the TTR case with care so as to not pinch wires.
However I will doublecheck if I open case again to confirm correct transplant of TW flywheel , source and pulser coils while exchanging neutral switch for known good switch from original TW engine.

Oil added to cylinder brought measured compression up to 100 psi indicated ( I believe correcting for elevation means would be about 130 psi indicated @ sea level )
After a few minutes another compression test indicated 70 psi.

All electrical items other than neutral switch come from the working Betty Boop when she was wheeled in for surgery. I doubt any of them failed in the installation, thus needing to ground out the sidestand switch seems odd since starter worked fine for first attempts to start.

Next will re-confirm valve lash & mechanical timing of valves relative to crank shaft. Do not know how to confirm electrical timing of spark pulse relative to crank shaft though. I did have to seat the flywheel using an impact gun to pull TW flywheel onto TTR crank shaft but assumed it all indexed correctly. I did not notice anything ominous as SKiPro warned about, just took some force to set flywheel.

A little busy now with a little localized flooding and mud-flows. Darn warm rain is melting snowpack again but now turning to snow once again.

I just want to further test the three legs of spark, fuel and compression before tearing head off for inspection. Betty's original motor sits in standby ready to donate, kicker, cylinder head, neutral switch, shifter, etc. as needed.
 

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No, 'cause I'm a Neanderthal.
I suppose a test for both would be to jump across neutral light's terminals at connection under seat grounding out the circuit. If switch is bad then neutral light should now come on when bike is in neutral. If starter then can engage when bike is in gear with clutch out then that would indicate a bad bulb in dash.
Any faults in my logic?
A/ jump across neutral light's terminals at connection under seat grounding out the circuit.
B/ If switch is bad then neutral light should now come on when bike is in neutral.
C/ If starter then can engage when bike is in gear with clutch out then that would indicate a bad bulb in dash.

Any faults in my logic?

B/ No, because the bike wouldn’t know if it’s in neutral or not, because you by-passed the switch — it (the bulb) will be either on or off permanently
C/ No, see condition B

It’s a fairly simple thing to switch the bulb over for one that you know works or even to find neutral with no light. If still no joy, simply by-pass the neutral switch as described, and carry on as normal without it

The more I read this (my) reply, the more elusive the understanding becomes, but try looking at this way — the bike doesn’t know it’s in neutral anymore, as the physical switch is no more, eliminated by the by-pass. This by-pass must affect more than just a bulb, otherwise when you blow that bulb, this would have the same effect. So, in theory, you are dealing with two feeds from the same circuit — hence my answer C/ No, see condition B
 

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Do not know how to confirm electrical timing of spark pulse relative to crank shaft though
Strobe timing lights are fairly inexpensive these days. With the TW, it will be useless as to adjustments, but it should show if the marks on the flywheel are correct to the spark ...
 

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I didn't read all the previous stuff closely so maybe it has already been said -- put some gas in the spark plug hole and then see if it starts.

Add'l Mickey Mouse story: I once had a single cylinder generator I couldn't get started. The plug was soaking wet. What I did, with the spark plug tightly in the hole, I took a propane torch and gently heated the area around the plug. It was barely warm, not hot. The paint didn't discolor. It started on the first pull. I think the warmth caused the gasoline to evaporate. Anyway, just an idea you might want to try living in a area that is colder than the inside of my refrigerator.
 
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