Avanti

[Adam_Winstone]

Capt.

Can't you just throw it together' like the rest of us do? (kidding)

Nice work.

Adam

[Blaginit]

Hi ya,I've just had a lightened fly wheel delivered but it's fins are half the size of my original it's bgm and was sold to fit a gp do you think it could cause a problem all help greatly appreciated if it is ok is fan cowl ok to use ps any one got a rear hub holding tool in bromsgrove area

[Captain Pugwash]

Hi ya,I've just had a lightened fly wheel delivered but it's fins are half the size of my original it's bgm and was sold to fit a gp do you think it could cause a problem all help greatly appreciated if it is ok is fan cowl ok to use ps any one got a rear hub holding tool in bromsgrove area

If you have a large Indian cowling then it won't be as good as it could be, if you can fit a thinner Italian type cowling it will be better.

You can make your own rear hub holding tool with a bit of flat bar (or you can use angle iron) with a couple of well placed drill holes and some bolts.

Mark.

[Captain Pugwash]

Too much Beer stopped progress on Sunday, I was hoping to get out to the garage but I failed.

Pressure test from Saturday.


If you do use a pressure test kit (leak test kit) always position the piston towards BDC.
I tried to make up for Sunday by heading straight to the garage as soon as I got home from work today.

I buretted the head, with the top end assembled and oil petrol 60/40 fed in through the spark plug hole piston at TDC.
This is a very accurate way to check the trapped volume and from that work out the compression ratio.






A volume of 24.2cc gives a slightly higher compression ratio than I had hoped for.

[Jamjo]

Hi Mark all I can say is I read these threads and follow what your doing , knowing I haven't really got a clue what I'm at . . But following these makes me want to do more . Fair play mate . .

[Captain Pugwash]

Hi Mark all I can say is I read these threads and follow what your doing , knowing I haven't really got a clue what I'm at . . But following these makes me want to do more . Fair play mate . .

Hi James, I'm not too sure I do know what I'm doing, I was originally going to just bolt it together in a day like I did with my last two Rapido engines.

But I had time and thought as good as the Avanti kit is I might be able to make an even better spread of power from lower revs with a few slight mods, but from that point on any progress seems to have gone backwards much faster than forwards
With me working away and only having every second weekend free and on those weekends I'm often riding a scooter and not spannering so it ends up on the back burner while other engine builds, the odd stator repair for mates and a little porting now and again seem to take priority.

[MickYork]

A vast there captain, any developments ?

[Captain Pugwash]

A vast there captain, any developments ?

Engines built strobed and all ready to run except for fitting an exhaust, I just haven't got round to putting it into my SX yet.

If the 200 engine that's already in the SX was running badly then I would have finished the Avanti sooner and made the swap by now.

But I will eventually

[Scooterlam]

What pipe are you going to run with this engine, Local lad just got 83 mph on a bog standard kit with an super tourer .

Will be interesting to see how yours goes.

[Angry Bloke]

What pipe are you going to run with this engine, Local lad just got 83 mph on a bog standard kit with an super tourer .

Impressive - do you know what gearing he is running ?

[Adam_Winstone]

4.8, was previously running 4.6 and not pulling this new top speed.

Adam

PS - Not me.

[Angry Bloke]

4.8, was previously running 4.6 and not pulling this new top speed.

Adam

PS - Not me.

Thanks Adam

PS - Not me either - couldn't get close ( but I am running an MBGM Clubman )

[Scooterlam]

I,ve seen 80 and cruise at 70+ on a AF road. more revs would give me more, but I might lose a bit lower down so ill leave mine alone.

[Captain Pugwash]

Don't think I'll see those speeds on mine.
But.
I have a good choice of exhausts to choose from including the MBGM clubman, Original Taffspeed, Taffspeed copy pipe, PM pipe and a franspeed plus a couple of other clubman pipes.

Going to try the original Taffspeed pipe first on tall gearing, then the franspeed on shorter gearing. See which gives the best power delivery.

[Scooterlam]

I tried the taffy copy,
Didn't do what I wanted, lacked the low down grunt for changing up on long gearing. Original taffy MK4 should go well.
I wouldn't be surprised if it was happy on 4.4

[Captain Pugwash]

A quick update,
I've fitted a Taffspeed Mk4 pipe for now and I'm pretty much maxed out on the gearing running 19x46 on a Pacemaker gearbox, approx 4.4-1 overall ratio.

I've had the engine running for a while now but I've not used it that much so can't really give much info.

Yesterday I had a power-jet kit fitted to the Dellorto PHBH30, what's needed now Is to dial in the jetting a little, I've left the power jet tube long so it sits mid of the carb inlet, I'm hoping it gets drawn on earlier, this is so that when I'm closing the throttle coming off power there should be more enrichment as the air speed over the tube should be greater than it would if it was shorter and higher up in the airstream.

Here's a few pics, sorry I never took any photos as the power jet assembly was being assembled and fitted.



A couple of pics showing how it sits on the scooter.







Big thanks go to Davet from this forum as it was him who built up the power jet kit and helped me fit it to the carb.

If anyone is interested in the Air filter that's on the carb, I can't really say much about it other than its very small and it fits onto the plastic bell-mouth and seems to be fairly free breathing, I will give some feedback later after I've done a few more miles.
This air filter may just fit under the panel on some Lambretta's, but it's going to be very very close.


Mark.

Oops!!! Though I had include this photo already. Showing the position and length of the power jet tube.



Better late than never

[Warkton Tornado No.1]

That air filter is very compact. If it flows well, that is quite a ‘find’ that hopefully can be shared….With a shortened manifold (to the maximum!) it may just clear the panel.

Is the power jet anything different to the norm, i.e Mikuni?

It appears to be just reliant on venturi vacuum, which is fine, rather than solenoid activated, which tend to vibrate to bits on a Lambretta engine.

It will be good to see how this all progresses.

[Captain Pugwash]

A few more miles covered on the Avanti, the running-in speed is up to 55+ with no issues up to now.

I've removed the small air filter and refitted the Ram-Air filter, the small filter is fine most of the time but if I grab a fist full of throttle to accelerate there is pronounced lag before the engine responds.

With the Ram-Air fitted the response is much better.

I also dont think the very light AF flywheel suits the Avanti, I feel it lacks the inertia the engine needs from the getgo.

Going to fit a heavier Indian machined down mid weight flywheel some time soon, I think it would be a better choice for this engine especially with the tall gearing 19x46 on a pacemaker gearbox, with a slightly heavier flywheel I expect the initial response to be much better plus it should give an improved slower tickover.

Also need to check the clutch assembly because on hard acceleration as the engine gets into the power I can feel the clutch starting to slip just a little, could just be somthings not quite right in there. Possibly needs stronger springs.

[Captain Pugwash]

I changed the flywheel from the AF light alloy flywheel to a machined mid weight SIL flywheel.
Here's a couple of pictures to help show the difference between them.










The larger and heavier (mid-weight machined) SIL flywheel weighs in at 1923g compared with the smaller lighter alloy AF flywheel at 1422g

There's only around 500g difference, that's about 1Lb in old money but I can instantly feel the difference between the two.

The heavier SIL has helped with the bottom end power delivery in first gear that's as I release the clutch and move off from a standstill. Now there's much more initial response and the tickover is much more even and slower than before there's also more engine breaking as I change down between gears.
But all that's come at the cost of midrange power delivery, before it was much more responsive as it came onto the pipe, but overall the Avanti seems to be an easier ride with the mid-weight flywheel.

A standard SIL flywheel weighs in at around 2500g or 2.5 kilos that's close to 6 Lb.

I'm going to fit an Ignition advance/retard, most likely a programmable kheper CDI.

[Scooterlam]

I run the mid weight, works well on mine.
I had the same clutch issues. Ron sells uprated clutch springs cant remember the make they worked ok. I went AF road clutch, the high torque and my heavy handed riding style made standard clutch borderline.
Although others have run standard 4 plate with more power.

How is it pulling 4th? I'm tempted to try ADV/retard but just put off by the variables it would introduce to cht/egt readings.
on the subject of which the Avanti runs better with higher egt readings on 17 degree static 7 plug and 600-625 degrees (usual caveat all readings are unique etc etc).

Also like your PJ position main seems very good with fixed jet very little leaning off in the over run but temps seem to creep a little at
1/3 to 1/2 throttle openings on prolonged running at those points and the lower position should see it working around there with out inducing bogginess on acceleration.

Good luck and keep the posts coming.