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Discussion Starter · #1 ·
Firstly, may I say Hello and Happy Christmas to everyone on the forum.
I have recently purchased a B1 rep, I'm very happy with it, and am enjoying researching and upgrading the Chinese err, quality issues :eek: So far, I have rebuilt the engine with SKF main bearings, SKF water pump bearings, 45cc big bore kit, and quality gaskets and seals. while i was in there, I also opened up the reed cage area of the crankcase, matched the case to the transfers, de-burred, knife edged and chamfered the transfer and boost ports, modified the back of the piston to open up the inlet passage at bdc and allow more flow to the rear boost port, along with the usual porting/flowing of the crankcase passages. i am using a stock rep pipe, with the first section modified internally for smoother gas flow. My question is regarding the small end needle bearing. the original bearing, is the width of the small end and has two thrust washers to stop the rod moving sideways. this looks to me to be heavy, antiquated, and prone to wear/lube issues as the washers block oil flow into the bearing. all other two strokes i have worked on (jap mx bikes) use washers on the big end to control conrod side clearance. everything i read, indicates i should change this to the later bearing, which i have, but have not fitted, as it is the width of the original part AND the washers. if i fit this, THERE IS NO LONGER ANYTHING CONTROLLING CONROD MOVEMENT. Bad idea. Can anyone tell me what the best components are for the small end bearing,?? :thumbsup:
 

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PBP SENIOR M!LKER
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Nice, goin for the gold.... The Small Conrod bearing? Are you talking the needle Bearings in the Crank? I'm thinking you are talking about the smaller piston needle bearing but might be a little lost.. On none of my Euro Bikes does it have washers on either side of that bearing.. How much play is there? Was it the only available bearing and where did you get it??
 

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Discussion Starter · #3 ·
Yes, its the small end bearing in the piston end of the con rod. it has about .5mm side clearance with the washers and original style bearing in. if you use the later bearing, it can only be fitted without the washers, then you can move the con rod nearly 3mm side to side !!! The Genuine Blata exploded diagam shows the washers, but the new blata bearing is designed to be used without them, i am wondering if the blata crank or the rod have been updated at the same time?
 

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PBP SENIOR M!LKER
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I'm no pro but I think the movement is ok.. I never pulled the cylinder on my WRS but I think all of my Polini pistons had a little side to side movement and no washers when I took them apart.. 3mm might seem like a bit much.. Maybe go to a specialty nut and bolt store and get some super thin 1 - 1.5mm washers if ur worried about it... I'm not sure if they updated that crank or not. Sorry. Someone here should know and chirp in soon.. Wish you luck!

Jon
 

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Yes, its the small end bearing in the piston end of the con rod. it has about .5mm side clearance with the washers and original style bearing in. if you use the later bearing, it can only be fitted without the washers, then you can move the con rod nearly 3mm side to side !!! The Genuine Blata exploded diagam shows the washers, but the new blata bearing is designed to be used without them, i am wondering if the blata crank or the rod have been updated at the same time?
You May also want to see if they have an updated piston that goes woth the new bearing.
 

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I am in the middle of modding my 46cc C1 engine, I was looking at all the side play also. My Rep 40cc Polini is the same way. I am going to get a 10mm Blata Euro bearing for the rod cause I put SKF bearings else where. Now that you brought it up, I will measure the play between the bearing ends and the piston. I was thinking a thin alum washer on each side.
hkmotos online has a $17.95 to your door, 50cc (46cc) piston kit with rings and pin & clips and bearing too I believe.
 

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First of all you should know the principle of the mounting and function crank/ conrod/ piston:

Generally there are two types of installed conrods:

- crank with bottom-steered conrod ( washers at the big end bearing)
----> no (needed) washers at the small end bearing/ piston

- crank without bottom-steered conrod ( no washers at the big end bearing)
----> needs washers at the small end bearing/ piston

so you see: every time only one steering for the conrod !!

( 2 steerings ( bottom & top ) are deadly !!!)


so you don't damage your parts ;)

I am in the middle of modding my 46cc C1 engine, I was looking at all the side play also. My Rep 40cc Polini is the same way. I am going to get a 10mm Blata Euro bearing for the rod cause I put SKF bearings else where. Now that you brought it up, I will measure the play between the bearing ends and the piston. I was thinking a thin alum washer on each side.
The 10mm Polini is not compatible with a Blata 10mm ; the outer diameter fromthe Polini is different ; you'll have 1mm air difference !!

The small end bearing for the 45ccm ( 39,5mm piston) is another one;
it's a little longer as the 40ccm ( 37 mm piston)

Possible by Blata rep 40cc - you can drive both ;
the standard one as also the ( little longer ) 45ccm small end bearing - is no problem but not vice versa .

Note: also all brands engines have no washers at the top !!!

Look at your crank and proof

The "air" , you'll seen between snall end bearing and piston eyes is normal ... se obove.
 
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