PK-Biest in der Tschechischen Republik

[msk_motori]

Hello! After 3 years of being on this forum and just watching from the sidelines, I want to create a small build project of my own. More precisely, really fine-tune my dream project.

I´m from Czech republic and as far as I know, I am the only idiot :D in our country, who wants to have a crazy smallframe. I have a German market PK XL with Quattrini M1L-56 which has broke down due to bearing failure on the secondary gearbox shaft. But before that happened I drove it for a few kilometres and the engine did not feel right. Before it gets to "power" or "ressonance in the exhaust" there seems to be a dip in the powerband and I don´t know why. Hope you can help me and sorry I´m writting in english, my german is not that great.

This is my setup
Quattrini M1L-R 56 (cylinder timing below) 
BGM 54/105 full circle crankshaft
Vhsb 34
Egig Taipan exhaust
Malossi 10-15-18-20
SIP reinforced clutch basket with 26/69
Bolla Elaborazioni XL2 clutch
SIP vape sport at 24°

 

[Spiderdust]

vor 35 Minuten schrieb msk_motori:

dip in the powerband

I'd assume the problem could be in the carb-jetting (first of all needle).

What about the squish?

[msk_motori]

Squish was 1.3mm for 54 stroke. I think that is too much. On 51 stroke the manual says 0.9mm. How much squish should I aim for? I think 1mm is adequite. 
 On the side of jetting, I have tried many combination - k57 k24 and also a lot of different emulsion tubes. I cannot remember all of the combination, but I think I should start to take notes 😅

[msk_motori]

Now I have it all dissasembled, sadly found a small issue. What do you think? Nicasil isn’t cracked, only aluminium is on it. 600 sandpaper to scuff it up and same on the piston and run it? The tolerance between cylinder and piston doesn’t seem like it changed.

Also, first time I have used the bread technique. I didn’t think it would work 😂

[karren77]

@bread: does it really work???would be awesome. 

[msk_motori]

Yes it does work! Find a M10 bolt and a soft bread and then stuff it inside, hammer it, stuff it,… repeat until the bearing pops out. 

[steven]

vor 5 Stunden schrieb karren77:

@bread: does it really work???would be awesome. 

Ja, habe damit ebenfalls Lager entfernt. Buttertoast bietet sich hier an.

[egig]

vor 16 Stunden schrieb msk_motori:

Hello! After 3 years of being on this forum and just watching from the sidelines, I want to create a small build project of my own. More precisely, really fine-tune my dream project.

I´m from Czech republic and as far as I know, I am the only idiot :D in our country, who wants to have a crazy smallframe. I have a German market PK XL with Quattrini M1L-56 which has broke down due to bearing failure on the secondary gearbox shaft. But before that happened I drove it for a few kilometres and the engine did not feel right. Before it gets to "power" or "ressonance in the exhaust" there seems to be a dip in the powerband and I don´t know why. Hope you can help me and sorry I´m writting in english, my german is not that great.

This is my setup
Quattrini M1L-R 56 (cylinder timing below) 
BGM 54/105 full circle crankshaft
Vhsb 34
Egig Taipan exhaust
Malossi 10-15-18-20
SIP reinforced clutch basket with 26/69
Bolla Elaborazioni XL2 clutch
SIP vape sport at 24°

 

 

The problem is the high blow down, on m1l i have same problems over 28° of blowdown , what are 56° of diffrenz trom transfer ports to exhuast port. and the best test that this is the problem you allredy did. 

 

Sometimes the reed valve can improve it , the rest is unless and wasting time.

 

you will get betther results with lower squish or very lean setting, but than you will destroi the cylinder. i alredy testet it many many times. 

[msk_motori]

vor 5 Stunden schrieb egig:

 

The problem is the high blow down, on m1l i have same problems over 28° of blowdown , what are 56° of diffrenz trom transfer ports to exhuast port. and the best test that this is the problem you allredy did. 

Ok, then how about this? I thought of a plan on how to save the cylinder. I measured the aluminium base gasket and it should have been 8mm but it is 8.3mm. I can correct this and the piston ring still wouldn't be able to pop out of the cylinder. 
Then I can use a small port-cutter to raise the ports about 1mm. If I do it correctly and good, the angle of the port shouldn't really change. I know the timing would be excessive but I think it could work better then it is now working. Which of these options would be best? If you have other ideas, I really welcome them. 

[egig]

Why is your instuction in german language but here you write english? 

 

But yes this is the correct process, but ceep atention to the angles and ceep the boost ports lower then the exhasust port, so dont touch the exhaust ports at all

[msk_motori]

It is because I know a few german words and I want more people to understand the drawings. Sorry, if it is a problem, I will only write in english. Still thanks for all your help. 

So option 1 it is! I will prepare for the milling and bring some results in the upcoming week.

[egig]

vor 4 Minuten schrieb msk_motori:

It is because I know a few german words and I want more people to understand the drawings. Sorry, if it is a problem, I will only write in english. Still thanks for all your help. 

So option 1 it is! I will prepare for the milling and bring some results in the upcoming week.

 

i asked only because, seems like you did less german gramatic errors than me 

[msk_motori]

So another year, another motor... 

I rode nearly 1000 km on this motor, but I should have known that the crank will give up... I heard that the BGM have a sometimes a bad pressfit and I think that I also overpowered the crankshaft. It's a shame I didn't have the time to measure the power. Anyway, It went with a BANG! Crank is done and so are the cases  and the cylinder is OK but the head and piston are dead!

 

  

 

But what now? I want to rebuild completely my PK, but before that I want to prepare (hopefully) one last engine with around 18-20 ps and test it. Cases are sandblasted and I need to decide on a cylinder.

 

 

I found cylinder for 240 euro and crank for 280 euro. What do you think of this setup? Are there any changes you would do?

 

2025 engine (18-20 ps)

VMC ET6-60 alu cylinder (126°-186°)

Fabbri Mover with ø87 crank halves (because I have a bored out side case)

VMC reed valve ø28-30 and modify it to 34mm 

VHSB 34

10-15-18-20 Malossi

27-69 with Fabbri basket
EGIG Taipan
Bolla Elaborazioni HP clutch
Vape Sport

 

Bearbeitet 20. April von msk_motori

[steven]

VMC reed valve is not available für PK frames. You need to cut and re-weld it.

 

For the price of ET6 and reed valve, maybe the italkast grv is an option. If your write to italkast, they can ship with PK intake.

 

34mm carb seems a bit over the top for me. I think 30mm YSN would also do.

Bearbeitet 20. April von steven

[msk_motori]

I already have from a previous project the VMC reed valve adapted to PK, so I wouldn't to buy another one. But I also think that the 34 carb is a bit too much. I have a PHBL 26 for a test but I think about the flat slide VHSH 30. Maybe I can try with the 26 for a change. It could consume a bit less. 

 

  

Bearbeitet 20. April von msk_motori

[steven]

Ok, great.

 

I also think you will need to cut the engine on the fan side a bit to fit the vmc cylinder.

 

ET6 is a great choice. I run the 60mm with longer stroke and it performes just fine.