G.B.ALIAN

I Have a K&B .61 Series 75Catalog # 6525 Standard Carb. Also have the Perry Pump #6535 And the Larger Carb. I tried to run with the pump. Could only run for short time.. I changed to regular carb, by-passed the pump. Engine ran great.. Only problem.. excessive fuel leaking from front.
Could it be the bearings??? I got on the Mecoa site and they show front bearing # 18-0002 and rear bearings Racing 18-8777 Standard # 18-0016. Also rear cover pre-1984 # 21-6101. Will these parts work on this engine. Thanks for your help. G.B. ALIAN...[sm=drowning.gif]

DarZeelon

Quote:

ORIGINAL: G.B.ALIAN

Could it be the bearings??? I got on the Mecoa site and they show front bearing # 18-0002 and rear bearings Racing 18-8777 Standard # 18-0016. Also rear cover pre-1984 # 21-6101. Will these parts work on this engine?

G.B.,


The front bearing is never the cause of this fuel/air leak, nor it is ever a good solution for it.

The front rotary valve is a part of the engine's intake timing system, which must either allow, or prevent mixture flow from the carburettor and into the crankcase, according to the position of the crankshaft.

For all practical purposes, if the crankshaft large journal is properly machined and to the right size, as is the surrounding crankcase, they must not allow much air to be sucked in, or much fuel leak out of the front of the engine.


If there is a leakage there, either the crankshaft, or the crankcase, in the front rotary valve area, is out of tolerance (normally a warranty issue - not in that old engine), or badly scored/worn.

A small fuel leak is a positive thing, since it will aid in lubricating the front bearing, if it is open to the rear.

If replaced by a grease-packed, fully sealed bearing (2RS), just leave it fully sealed and it will outlast your engine...


A more noticeable leak cannot really be fixed using a sealed bearing (fuel/air will continue to leak around it...), but its magnitude will be reduced... Go to [link=http://www.rc-bearings.com/]Paul McIntosh at RC-Bearings[/link].

His site is currently being reorganized, so you will need to E-mail him through there.

An R6-2RS bearing (two seals, grease-packed) will only cost you $3.97... Just $3.97!!!

Don't be suckered into paying that humongous charge for the same bearing, as quoted in that other site you mentioned in your post...

Flyboy Dave

My Feedback: (21)

.....I have a different opinion. If I went to all the trouble to teardown and rebuild my
K&B engine....which can be a pain sometimes....

.... you wouldn't catch my puttting four dollar bearings in it....I can assure you of that !

FBD.

rainedave

My Feedback: (1)

Those wrist pins can give you trouble.

Flyboy Dave

My Feedback: (21)

....yep. Some old liners give no joy as well. [:@]

I wouldn't put a four dollar bearing in a roller skate.

FBD.

buzzard bait

FBD - you don't understand, it's not that you're getting a "cheap" bearing from Paul McIntosh. It's just that you aren't paying a premium for a name. The others will charge you like the manufacturers charge for engine parts. But there is no need to pay such prices for bearing because they come in standard sizes for a variety of uses. Paul charges you for a standard bearing that fits your engine. Don't make him think he has to charge more to get business! Jim

DarZeelon

Quote:

ORIGINAL: Flyboy Dave

.... you wouldn't catch my putting four dollar bearings in it....I can assure you of that !

Dave,


But if you do buy those rubber sealed front bearing for $19.95, you actually would be putting a $4 bearing in your engine...

Or in reality, at the source, it is a 20-30 cent bearing...

Those bearings are the same and both RC-Bearings and Boca have the same Chinese sources.


It is just that Paul McIntosh believes in giving you a fair deal and the other guys just regard you as a consumer (...) that must be shaken penny-less, while making him 'think' he got a 'great deal'...


I am sure you are not that stupid...

EDIT: Typo.

TimC

Dar, do you have a link to show that both Boca and RC-Bearings use the same vendor. As far as I know, those Communist Chinese bearings have no markings.

DarZeelon

No link, Tim, but in the past Boca used to show the country of production on each bearing's web page.

They have stopped and I do have sources that I talk with...


Neither of the hobby bearing dealers will actually disclose the name of the manufacturer(s) they buy from.

But as to the sources and the actual costs, I know them for a fact, but as a good (former freelance automotive) journalist, I would never disclose my sources...

Flyboy Dave

My Feedback: (21)

.....name calling already, DarZelon ?

NM2K

My Feedback: (14)

I have dealt with Paul McIntosh (RC Bearings) over many years. He is an honest and reputable man. He does not sell junk at any price point.

Paying more for something does not necessarily mean that it is any better.

That's my different opinion.


Ed Cregger

blw

My Feedback: (3)

There was an old business adage that stated you had to make something for 10% of what it sold for in order for your business to be a success. This was years ago before our current levels of imports. Just tossing that out for thought since some form of the rule would still apply. I always wonder about it when looking at engines from all the places in the world like Japan and China.

G.B.ALIAN

Thanks to all of you for your input about my K&B .61. The response was more than I could have even thought of receiving. I enjoyed your comments to each other as well. I sent an e-mail to Paul McIntosh about the bearings and hope to hear from him soon. Thanks again. G.B.Alian

proptop

My Feedback: (8)

FWIW you need a 6902 rear and R6Z (or a rubber sealed one if you prefer ) front bearing...

RC-Bearings

My Feedback: (1)

Actually, I WILL tell you a couple of sources that I used. Fuzhou Basico Bearings and Fuzhou New Power Bearings. I don't use them any more because their minimum orders are too large for a small company like me. Both provided excellent quality, prices and customer service. The days of blanket statements regarding Chinese quality are long gone. Just like your dad used to say about Japanese quality in the '60s.

The reason you normally don't see markings on Chinese bearings is that they are OEM manufacturers for the most part and we are just piggybacking on that massive market. I looked at having my logo laser etched on the bearings (RCB) but then I would have to raise prices and you wouldn't receive any benefit from that.

The Chinese manufacturers have invested great sums of money to modernize their factories and i believe that if they chose to, they could make a serious dent in SKFs and NTNs business in very little time. They tend to focus on the economy end of the market because that is where the volume is. Most of the bigger Chinese factories put out MILLIONS of bearings a month. Most destined for western manufacturing markets.

NM2K

My Feedback: (14)

Your thread has helped me too. I have five or six K&B .61 engines that I have acquired (used) over the last while. I plan on rebuilding them all at once, after an antifreeze session or two. Some of the guys on this forum are real pros and they know about the different models of K&B .61 that have been made and their particular quirks.

I have seen certain stock versions of K&B .61 engines that would blow your mind. They really rev up and produce the power while spinning usable pattern props. The later versions were detuned to the John Deere tractor engine range and were good engines, but they didn't yell like some of the earlier versions I have owned/witnessed. I'd love to know how to tell these engines apart and whether I can still find parts for them. I have no idea of which stage of tuning the new K&B engines have been made. I do have a fairly new K&B .61 that was made after Randy's purchase of K&B, but it is the least expensive ringed version. Again, since I haven't ran it, I have no idea which version it is. Even the docile engines are very useful, so I'm not worried about it. I'll have a use for it, no matter what.

As I understand it, the K&B's weak spot is the crankshaft. The basic engine is capable of delivering a lot more power, but the crankshaft cannot handle it. I forget what the outside diameter of the crankshaft is, but I believe it is stuck back in the 12 to 13 mm size, which is part of the problem. Later schnuerle ported engines ran 15mm crankshafts and later some expanded to 17 millimeters.

While there are some really strong .50 class schneurle engines offered today, there is just something magical about obtaining the same, or better, flight performance from an engine that was released in 1972. They were stalwart, trustworthy and powerful engines for their day. The Super Tigre G60 Bluehead unseated them from their brief period at the pinnacle of pattern engines. But they were there for a short period of time, in the USA. Simultaneously, HP's four-bolt 10cc engine, was reigning supreme in Europe. The K&B .61 was the last baffle piston engine to hold the pattern crown.


Ed Cregger

DarZeelon

Quote:

ORIGINAL: Ed Cregger

...I forget what the outside diameter of the crankshaft is, but I believe it is stuck back in the 12 to 13 mm size, which is part of the problem. Later schnuerle ported engines ran 15mm crankshafts and later some expanded to 17 millimeters.

Ed,


This K&B engine has a 15 mm diameter crankshaft large journal.

The bearings normally used in this engine are R6-Z and 6902, the exact same sizes used in nearly all .40-.56 engines out there.


MVVS .61-.91 engines also use a 15 mm i/d rear bearing, but there it is a much higher load capacity 6002 bearing; not the 6902.


But as you wrote, it is the crankshaft and not the bearing that is the 'Achilles' heel' of this K&B.

blw

My Feedback: (3)

The crank pin is the weak area.

proptop

My Feedback: (8)

The older ones have a pressed in crank pin and they can loosen and come out after prolonged and/or repeated high r.p.m. use. (the 6.5 comes to mind here ) Is that what you guys are talking about?


I aquired a large "lot" of parts thru *bay that had a couple of one piece K&B .61 cranks though...I'm thinking that they are a newer version?
Does the latest MECOA version have a 1 pc. crank?

Phil Heller

My Feedback: (9)

Hi Ed,

The KB61's converted by Clarence Lee can hold their own against any of the schnuerle ported 61's sold today!

Phil

blw

My Feedback: (3)

He still cautions against excessive RPM and crank damage.

G.B.ALIAN

Hello PROPTOP. Thanks for your info on the part numbers for my K&B .61 bearings. I took the engine apart and the front bearing shows R-6Z. The rear looks like 9302 K. The number you gave for rear was 6902. I haven't removed the rear bearing from the case yet. I don't know how to remove it...any ideas???. Also any input about the rear bearing numbers. Are there any cross reference numbers showing 9302 K??? Thanks G.B. Alian

proptop

My Feedback: (8)

Hi G.B. welcome to RCU
Here's a page with the bearings listed for the .61 (for some reason, they have it as a FIRE but as we know it's a FISE )

http://www.bocabearings.com/main1.as...ide&pg=2&mfr=3
( I tried rc-bearings, but got "dropped" off from the site...? Will try again...)

I get "no results found" for a 9302 bearing, and have never seen/heard of one in a K&B .61? I currently have 6 of them, and have had several more, and they all have had a 6902 rear bearing...

As far as getting the R. bearing out, there are a couple of methods.
You need to heat the case...
Edit: Actually, it would probably be better if you did a search on bearing removal/changing, because I am getting "timed out" for some reason, and won't have time here/now!?

DarZeelon

Quote:

ORIGINAL: G.B.ALIAN

...The rear looks like 9302 K.

G.B.,


Metric bearings are closely numbered by size.

The 6902 that we gave you here has a 28 mm O/d, a 15 mm i/d and is 7 mm wide.

If the number was 6903, the bearing would have 'grown' to 30 x 17 x 7 mm, which is common in some older .60-.61 engines.
If the number was 6901, the bearing would have 'shrunk' to 24 x 12 x 6 mm, which is common in some smaller engines.



One company uses slightly different denominations... The Swiss WIB company (the best racing bearings you can get) calls their bearings of the same sizes 61902, 61903 and 61901 respectively, but they have the exact same dimensions.

The 6902 and 6903 have the same ball specs (Imperial 5/32" - 10 and 11 balls respectively).
The 6901 has 10 1/8" balls.


The number you had specified does not exist in bearing manufacturers' 'search' pages...

G.B.ALIAN

Hello This is G. B. Alian Thanks to all who had comments and info regarding my K&B .61 bearings. I was able to remove both the front and rear bearings. The front was R-6Z. The rear Showed 9302-K. The 9302-K matched the 6902 in size. I ordered the bearings from Paul McIntosh and should be receiving them soon. I will keep you posted as to the results with the new bearings. Altho there were some comments about the bearings not being the source of the problem, I still wanted to see if there would be any improvment. I'll let you know.. Cajun Gators Flat Bottom RC Swamp Boats Rule On The Bayou