Need help, AF05E engine with 46mm BBK, no power.

[Rogerio]

Hi fellows Spree addicts,
I'm back on my NE50 (Elite SE50P in USA) after an engine rebuilt (new rod, balancing crankshaft, new bearings, etc).
It runs fine in idle, but when hot, at 1/2 throttle it has no power and engine makes a funny noise
My configuration is:

AF05E engine.
BBK 46mm, 62cc.
Original Carb.
Jet increased to Malossi 273582 0,87mm (original was 0.8mm hole).
Original air filter with few extra holes.
No changes on oil pump/system.
Plug BPR 8 HS.
Exhaust as pic.
Final reduction Malossi 8:1 (original was 11:1).
Variator rollers 7,5 grs.

I need your advice to put my Honda back on road with a decent behavior, I've checked the BBK jet sizes on Wikispredia and it seems that mine 0.87 mm is too small!!!!
Kind regards from Portugal (Europe).

[paulpauly7]

you really need a aftermarket carb and manifold a polini 19 mm would be great.I believe your problem is jetting and air flow .Also if your rollers are too heavy then it will never be able to rev up to its power band .

[Wheelman-111]

Greetings, R:

We don't see the Euro engines very often here, and it's hard to know if your "original" carb is anything like our PA series. Therefore jetting size questions may not compare across the ocean. Our PA carbs came with .78, .82, up to .88 mm main jets. Even the Spree ran at least a .65! It's safe to say that installing a BBK immediately requires a larger-than-stock size but how much larger is tricky. A lot depends on the air filtration system, too.

For sure you should get a Cylinder Head Temperature gauge without delay, if you don't have one. Meantime, show a picture of the spark plug, which will give a clue as to the overall operating temperature.

[Rogerio]

Thanks Wheelman for the reply,

I made a mistake on the above jet sizes: My original jet was 0,8 mm and I've replaced it with a slightly bigger one (Malossi petal Kit 273582).

Plug (BPR8HS) picture is as follows, after a ride of 20 min.

I've already replaced the CDI, but nothing changed. After a BBK the CDI needs replacement (timing alteration)? Is there a rev. limitation on the originals?

Kind regards

[curtis966]

No the CDI does not need to be replaced. Stock is just as good if not better then most aftermarket ones other than maybe the malossi cdi. And there is no rev limiter on the stocker. Looks a little rich on the plug. Was that new before the 20 min ride? Grab a fresh plug and run at WOT for about a half mile and hit the kill switch and hold the throttle open untill you come to a stop and pull the plug and check it. That will give you a accurate reading.

[Rogerio]

Hi Paul,
Thanks for the hint about rollers weight, I've checked, mines have 7,5 grs. and yes, when running at full throttle max. rev is not reached but if I accelerate with the rear wheel above ground it reaches much higher revs . What do you suggest for the rollers weight with my configuration?
Regards

you really need a aftermarket carb and manifold a polini 19 mm would be great.I believe your problem is jetting and air flow .Also if your rollers are too heavy then it will never be able to rev up to its power band .

[Wheelman-111]

Greetings:

I re-read the thread and have the following advice:

1. If you're running the stock pump alone, STOP! You increased the displacement by over 20%, so that shiny new 46mm big-block will require something more than the pump alone can supply. I recommend you add 1% pre-mixed fuel with 2-stroke oil. Graphie may be right about the wrong oil in the pump. It's cheap to drain the oil tank and refill with a known brand of injector oil. Better still, get a plug to replace the pump and run 32:1 (4%) premix only. You have to pre-mix anyway so...

2. Rollers apparently need to go down from your current 45-gram total load. Try 39 grams and see if you like it better. Those tall (Malossi Primaries?) may be 8.83:1, and immediate from-0 acceleration is sure to suck anyway, but at least you'll move better from 15KPH on up with the engine singing a higher note. Another way to raise RPM is to substitute a stiffer center spring. Polini or Malossi can help. It is possible that the 62cc engine doesn't have the cojones to pull 8.83 gears to maximum speed no matter what you do, but acceleration AND top speed should both improve.

3: A better carb, as Pauly suggested, is a good idea. Adapting Polini or Dell'Orto is a bit of a hassle, but Arreche-for-Honda carbs that fit perfectly with the AF manifold were available in Europe as recently as 2009. Throttle cable, bystarter, everything is bolt-on. 19mm or 21mm is a good choice. With good tune and fair winds (Or a downhill...) the AF05 modified like yours should approach 100KPH.

[Rogerio]

Thanks Wheelman a lot for the professional advices:
1) Of course and logic, 20% increase in bore needs more oil. I'll add 1% 2T oil in the tank.
2) I've ordered the 6.5 gr rollers, I'll let you know the result.
3) 100KPH It's far above my goal of 80KPH, and at that speed you need at least "carbon brake disks" to stop these little marvels .

Kind regards

Greetings:

I re-read the thread and have the following advice:


1. If you're running the stock pump alone, STOP! You increased the displacement by over 20%, so that shiny new 46mm big-block will require something more than the pump alone can supply. I recommend you add 1% pre-mixed fuel with 2-stroke oil. Graphie may be right about the wrong oil in the pump. It's cheap to drain the oil tank and refill with a known brand of injector oil. Better still, get a plug to replace the pump and run 32:1 (4%) premix only. You have to pre-mix anyway so...

2. Rollers apparently need to go down from your current 45-gram total load. Try 39 grams and see if you like it better. Those tall (Malossi Primaries?) may be 8.83:1, and immediate from-0 acceleration is sure to suck anyway, but at least you'll move better from 15KPH on up with the engine singing a higher note. Another way to raise RPM is to substitute a stiffer center spring. Polini or Malossi can help. It is possible that the 62cc engine doesn't have the cojones to pull 8.83 gears to maximum speed no matter what you do, but acceleration AND top speed should both improve.

3: A better carb, as Pauly suggested, is a good idea. Adapting Polini or Dell'Orto is a bit of a hassle, but Arreche-for-Honda carbs that fit perfectly with the AF manifold were available in Europe as recently as 2009. Throttle cable, bystarter, everything is bolt-on. 19mm or 21mm is a good choice. With good tune and fair winds (Or a downhill...) the AF05 modified like yours should approach 100KPH.

[Rogerio]

Hi Graphite,

The engine oil is 2T Sunoco 1/2 synthetic, the plug thread on the pics has copper grease.

looks like your running motor oil to me. Look at all that buildup, and the oil in the case is brown.

[Wheelman-111]

Greetings:

Si, better brakes would be a Very Good Idea. If you don't wish to/can't cut, weld, hack up your plastics to adapt a decent front disc, you can at least take a large step in the right direction by adapting a Metropolitan (Giorno? Super-Happy Fun Grin? in your neck o' the woods?) front rim and 95mm brake panel. Far and away superior to the 80mm you probably have. Even for 80 KPH, a very worthwhile and (here at least...) affordable bolt-on change.

[Rogerio]

Yesterday made my road test with 6.2 gr variator rollers and 1% oil in tank. I've got more rev's at medium speed and less power at low speed.
But my main problem remains, no power with warm engine (after 5 KM), it seems a bad ignition timing

[1man8scoots]

How does your piston look? No power when warm on a 2 stroke usually means bad head gasket. Or at least an air leak.

[patthesoundguy]

You need a temp gauge! You may be too lean in the bottom end so once the motor is warmed up and I'm guessing you have an auto enrichment set up like a bystarter and it stops enrichment by the time you get 5km down the road its lean in the bottom end. Try setting the idle air screw in further for now to get richer on the pilot circuit, it my need to go all the way in before you get some results. That's why an aftermarket carb is really needed with a big bore kit. You also have an aftermarket pipe on as well? The pipe can drastically affect where the power band is, usually up higher than the stock set up. So there are a few variables you have have to deal with and they all affect each other. Big bore kit needs a bigger carb with a replaceable pilot, then the pipe shifts the power band up thus needing the tans to be tuned with different clutch springs, centre spring, and rollers.

[Wheelman-111]

Greetings:

Do not worry about ignition timing; it isn't the problem and even if it is, there's not much you can do.

Trans tuning and jetting correction is needed. With light rollers, it is possible for the pulleys to start shifting before the clutch engages, resulting in that "2nd gear start". Fire it up on the centerstand to see if that is happening. Temp gauge is a critical tuning tool, as PTSG suggested. As he also said, you can richen the low end by fully tightening the air screw, and see if it is better. On top you must take care not to go too lean - spark plug appearance can guide, but a Cylinder Head Temp gauge better. You may be too rich OR too lean. Both reduce power but lean can cause damage.

[patthesoundguy]

thats a great idea wheelman to run it on the stand to watch the trans do its thing. i struggled with the "2nd gear start" on my aero 80 for a while until i ran it with no trans cover on, and noticed the driven pulley doing its thing well before the variator had a chance to do its thing. turn out the centre spring was totally worn out.