Modern Vespa

Have been looking around for a nice temp guauge for some time, but also wanted a rev-counter built in…
Ended up going for this Polini guage which I fitted today……

Nice… very readable. Curious to know max revs and temperature
Thanks for sharing

Too early to give you any useful info as Im not run-in yet, but I will post some info when its done a few miles…
Cheers…

Wow. Nice one. Where did You find it ?

SIP have them and are the cheapest from what I have compared.

https://www.sip-scootershop.com/en/product/rev-counter-polini_P1711001

Havent had much time to do the full run-in yet and Im still running rich.
But I noticed an oil leak from the cylinder base gasket?

I initially fitted everything, then before starting the engine removed the cylinder and head again to check squish.Refitted again using the first base gasket. So used the head and base gasket twice after torqing down.
Is this a no-no? Or can you use a head & base gasket again if the engine has not been running?

I retorqued the head after a few heat cycles but still some small leak of fuel/oil.

Anyone using sealer on the base gasket?

Cheers Robbie

Yes, everybody who doesn't want it to leak

Cheers Jack..
OK, Then next time I will add some high temp gasket silicone to the surfaces…

Silicon expands into the transfer ports and doesn't wash away. Won't slow it down much but won't be faster. Better to use some non setting sealer.

Robbie,
Just to clarify.
1. Best option for base gasket sealer is the "bonds". Threebond, Hondabond, Yammabond.
Here in the US - you can buy Hondabond at the car dealership parts counter.
2. You can use and re-use base gaskets.
3. I suspect you might not have a leak. A leak would show itself with a pressure test. Did you do that? Essential when building these motors. Easy to execute.

What often happens, when you run very rich, is that oil will come out from the exhaust stub where it connects to the exhaust pipe. This will run down your cylinder and may look like an oil leak.

Are you sure your cylinder is actually leaking. - and it isn't just the motor being run extremely rich?

Thanks Charliemann,

1) OK clear so no silicon type sealer. I will try snd find one of the three you mentioned.

2)Wasnt sure if I could reuse the base gasket 👍

3)No I didnt make a pressure test. I took care when putting it together but your right, I should have made a test before fiting it to the chasis.
Im not sure its losing pressure, just weeping a little from either the base or the exhaust stub.
And yes as you said its running really rich so maybe Im worrying about nothing 😜.

I will clean the area, Reduce the jetting and see how it looks.
With the exhaust stub leaking do you use exhaust sealer or just ignore it after its torqued down?
I already dremmeled the inside of the exhaust header pipe with a sanding wheel slightly as it would not fit the cylinder stub otherwise…
Even then I needed to add a little grease and bang the exhaust header a little with a rubber hammer a little….so likely coming from there…

Thanks for your advice…

Have a look at the various home made contraptions to check for air leaks.
They are fairly simple to build from a cheap blood pressure gauge and a few pieces of tube and rubber.
Only thing you have to remove is the ex. pipe and the carb & carb box - to perform.

No amount of care - unfortunately - can confirm no leaks.
It only takes a microscopic crack to allow air through.
But that doesn't mean you have one.
Just saying - its possible no matter how much care and the only way to really know is with some form of leak test.

If you are seeing ok temps, and no signs of detonation with your piston - I wouldn't fret about it yet - but rather continue to walk down the main jet until you have it tuned in - and see if the oil leaking goes away.

The symptom you describe sounds mostly to me like very rich jetting.
Keep us posted.
-CM

Thanks CM….I will do as you say. The motor does run well, so maybe me worrying about nothing.
Im noting down the temps and making an Excel sheet with all the jets, slides, Atomisers etc and seeing which runs best and with the coolest temperature.
Cheers Robbie

Temp is one good indicator.
Plug color is another.
If you own a cheap scope camera to look at the piston top through the spark plug hole, that is also helpful.

Do you have an area that will allow you to run WOT in 3rd?
Doing this, shutting off the engine, coasting down to a stop, pulling plug, and shooting picture - will allow you to determine if you have your main jet correct: when time comes.

Jack has your back on that.
Just kee in mind, your plug will change appearance quickly, so you don't want to idle or ride slowly just prior to shutting off the motor.

If not clear - ask and we can clarify.

Re-cap your exact jetting set up and when you're happy its run in enough, start reducing the main jet.

Initially short WOT runs in 2nd and just feel the rpm does not reach maximum. It will splutter as held open and it tries to rev higher. reduce the jet one at a time until the spluttering at WOT just stops.

That Excel sheet would be interesting to see.

You asked a while ago about my bolt-in sensor temps. I'm getting max 165-170 now on 2 bikes, which corresponds to 310 or so using a sensor under the plug. Max-max 400, which was a brief fluke. No scoring on the piston after that fluke.

Highly recommend replacing the split/flat washers with Nord Locks on the bolts.

Cheers CM

Yes I can manage a WOT in third and I can check the plug.
I still want to do some miles around town before I start getting some higher speeds on the country roads.
I also want to try the WOT on this over-rich main that im running and see how the temperature looks. But first a few more around town easy miles.
Then I will down-jet to one jet lower.
Should have it run-in this weekend then I can start the fine-tuning…

Cheers Jack
Will Do…

You mean there was such a difference in temp when measuring from the spark-plug washer compared to the thread in the cylinder-head? Thats crazy?
Was it the same guage?
I think you are running the SiP speedo right?

I will let you know what temps I am getting.
The great thing about the Polini gauge is you can set several different LED colours as warnings for different temperatures and it also records the max temp and max rpm for each ride that you make…

Thanks Ray for your tips..

Ray and I have both confirmed that the temp gauge screwed into the head vs the ring under the plug is very different.
Same gage.
I simply unplugged one and moved to the other - and found about 50° change between the two. My 290° on the spark plug ring is 340° from the in head sender. ( I had them both on the head - and just unplugged one and switched it to the other. it was repeatable).
Ray can comment on his experience.

I managed to get some miles in yesterday and finally could give some WOT.
I got a max temp at WOT of 178 celsius which is about 350 Fahrenheit with the sensor in screwed in the thread.
I was at about 65 mph and 8000 rpm. Still a little rich but Im ok with it as it splutters slightly in lower to mid rev range, but I can live with it.
Still to do a plug chop but I know its still rich.
On my next ride I will do a plug chop and post a pic.

Normally it will run around town or on country roads at about 140 celsius (245 Fahrenheit).

Initial thoughts are why is the gearing so low?

The WOT temperature doesn't correlate with the crusing temperature. The main jet is either way too big or a bit too small. Fuel starvation? Or could be too much timing. It's not ok to leave it there.
Sue it was nice to get it moving though.

Thanks Jack..
Timing is at 19 degrees the same as the Pinasco was..

I have a fast low tap and the carb drilled out. But im having issues that when the fuel is low say 1/3 full the engine stops and I need to wait a little for the carb to fill again but once the tank is full or above 1/3 then there is no issue. I think i need to reduce the length of the fuel hose, but I cut it to tne recommended 60cm. Seems like a pressure issue...

I will get the fuel line sorted and see if this helps?

19 degrees static is strong. I would move this to 17, until I knew it could take more.

If you get fuel starvation under 1/3 tank, then you are still getting it on a full tank. Just not enough to stop the engine or change the situation.

Hose is the correct length but is it anti kink type? Is it 7mm minimum ID? Any fuel filter? When you think you're done, take it outside and run a whole tank into a bucket. Should take less than 4 minutes and flow to empty (switch to reserve when it gets there).

Cheers Jack

Ok I will try 17 degrees

Its not the anti-kink type but I have a length of anti-kink 8mm id in my spare-parts if i remember right.
I have No fuel filter.

I Will exchange the hose…

Whole tank time will be longer without a pump. Better make that less than 15 minutes on gravity.

Which fast-flow tap are you using?
If it's a BGM, welcome to the engine-dying club!

Btw sorry, the max temp I posted above is a typo(not Celsius). Should read 365-370F. Urban cruising 265-280F. A few guys posted 185-190C on the BGM 177 FB group.

Thanks Ray
Funny you say that as I just dumped the BGM fast-flow tap for a SIP one. I wrongly ordered the BgM without reserve, so only on and off. But at about 1/3 of a tank it didnt deliver any more fuel. I made a test with the Sip Tap and it delivered fuel with the same amount that the BgM tap stopped delivering fuel. So the BgM tap is rubbish 👹. Well the one I got anyway.
But as Jack mentioned its better I also replace the Fuel line to avoid kinks.

I had some addition issues after my ride yesterday. On the way home I noticed no blinkers, no headlight, no fuel guage no speedo light.
When I checked the headlight and park light the bulbs where blown,,so I suspect the high revs on the ride blew the bulbs. Probably the regulator/rectifier is faulty.
Always something to fix on these Vespas 😝