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Discussion in 'Battle Scooters' started by GotMojo, May 21, 2019.
It looks like it could be a Paul Jr. chopper.
Hey kids, long time no see!
Project stinky has been on hold for a while now. I was waiting to see how things developed on the cannonball front. The wind was let out of my sails and I kind of lost interest once it was clear that it wasn't likely to happen. Remember, I've been getting ready for over a year and a half now. Loss of interest was bound to happen, right?
In any event, the bike isn't finished. There are still 3 big ticket items left on the list:
1. Fix the seat
2. Fix the fork seals
3. Fix the engine.
Wait, fix the engine? What did you do???
We'll get to that, we'll get to that...
OK, let's get started!
Item 1: The seat
When we last saw the princess, she was sporting a brand new Utopia backrest. After a few turns in the neighborhood, I realized that it was too far forward and would prove to be uncomfortable for long periods of time.
Unfortunately, it doesn't have any way to adjust the offset, just the tilt angle.
It's kind of a dumb design but was the only real option available at the time.
How to fix? We hit with large dose of stoopid, naturally.
I don't know how to weld. I don't own a welder. How much is this going to cost??
If you guessed 'exactly 1 12" pizza', you would be correct. Neighbor kids were welding some crap in the garage and I happened to be making some pies on the same day.
Set the whole thing back about 2". Plenty of clearance now.
So, what's going on with the engine?
Well, ever since I ripped out the malossi forcemaster, the engine has been bogging down under acceleration. It builds power, bogs, builds power, bogs until it gets up to speed. I figured I damaged one of the connectors when I was in there last. My #1 suspect was the ignition cable/coil.
The Rolling Circus Bear (@villageidiot) was kind enough to donate a new cable with a coil clip. It came with also free dose of "you're overthinking this" when it came to ignition cables. Turns out that making a new one is so simple event a moron like me can tackle it. The cap just screws onto the cable!
Sorry no pics of said cable but I do have an action shot of said circum ursi.
Where were we? Oh, that's right. Changing the ignition cable.
It didn't work.
So I took the next logical step.
That's right. Mr. wannabe mechanic went straight for the valves.
They were super-tight. Why???
Flywheel TDC mark is ok.
Your mechanic is an idiot!
Engine was spinning freely so I don't think anything got damaged.
Has it been that way the entire time, since you built the engine? Four teeth is a long way off. There is a thread on Modern Vespa from someone who jumped his cam timing 4 teeth and the exhaust valves just barely touched the piston. The marks in the carbon were plainly visible, but he leak checked the valves and they were sealed. It jumped because he spun the engine without the variator installed.
The way it sits in that photo I’m guessing the low and midrange was lacking, and ok in the higher rev ranges?
Good to see you back, always entertaining.
way to dig into it Jose.
i hope the mechanicals of the engine are ok.
not arguing, but curious....
what would the variator have to do with cam timing?
i ask because i ran mine for a minute without the variator on last weekend so i could build up engine temp/coolant pressure.
Yes, what I suspect is that I did in fact align it but didn't tension the power side and when I installed the tensioner, it rotated.
There's always been power but it's been 'off'. I attributed it to the forcemaster but in retrospect I think it was a red herring.
Without the variator installed the crank has way too much end play, and can misalign the timing gears. This puts excess axial stress on the chain and causes it to jump.
It happens often enough that there have been multiple jumped timing/bent valve threads on MV over the years.
fair enough. Hope I didn’t fuck mine up!
Since you are having the valves adjusted by someone well-experienced with the product I would imagine if cam timing is off he should find it.
I had no idea that running the engine without the variator was a bad idea. Is that limited to Piaggio products? I've done it on Hondas many times with no issues, but maybe I'm just lucky?
I don't know, and I can't say if it affects all piaggio products. I just know that it's been posted about repeatedly on MV about large frame vespas. Any engine in which the variator must be bolted to the crank to control end float could potentially have this issue. My answer is to not run anything without the variator installed.
The other end is bolted down to the case. The crank isn't loose and isn't going to start rattling around.
He's didn't run it for a long time and it wasn't under load. It will be fine.
I could see some mechanics not looking in the inspection port for TDC and just setting the cam gear on the 4V mark and adjusting the valves.
This one is a good example of how little running time it takes. His jumped enough to quit running, but luckily the valves didn’t touch hard enough to bend. He was very fortunate.
If the timing didn’t jump far enough for it to quit running, I agree he probably didn’t hurt anything. But that doesn’t mean the cam couldn’t have jumped a tooth.
Well, I think I figure out the problem.
To recap, it wasn't:
The fuel injection controller
Spark plug cap
Spark plug wire
Nope, it was none of that. By the process of elimination, I found the culprit for my poorly running princess was none other than:
I threw in 1/2 a gallon of fresh gas and all of the hesitation and bogging down went away.
I spent 3 months of agonizing about an imaginary catastrophic situation. Ignoring and avoiding dealing with it at every turn.
Sometimes even when you win, you lose.
Looks like the princess will be getting around this summer after all!
surely the cam timing had something to do with it, no?
Made no difference, believe it or not. The marks were off to be sure but I think what I photographed was after adjusting them to line up again without properly tensioning the chain. At this point I have no idea where it was when I started, only that they didn't match. Maybe off by 180?
In any event, I'll check the valves one more time, get her buttoned up and proceed to get it ready for a race that isn't going to happen.