Just bought a used bottom end and have a few Q's

[dtek01]

I just got a lighly used (still 1st bore on cylinder) 88' bottom end. All OEM and never been apart as far as I can tell and looks great.

How can I tell if the crank and bearings are good without splitting the cases? Is there way?

How much crank sideplay is acceptable and is there anything else to look at?

It has some very slight movement when I grab the flywheel snout and wiggle it around up and down side to side.

I plan on putting my 295cc PC2000 cylinder on it after getting it repaired from a crank faliure so I am a little paranoid now.

[C-LEIGH RACING]

When you say side to side play at the flywheel, how much, can you see the movement with your eyes or your feeling it with your hand.
If you can see the movement with eyes, probably best to pull the bottom end apart & replace some bearings.

This is just a guess, depending on how much play (wear) is in that main bearing.
A new main bearing on the flywheel side, you cant see any movement at all, but if you try & move the flywheel & realy try to feel it, you can feel the clearance between the ball & race.
Neil

[dtek01]

Thanks Neil,

Well i can see it move so it looks like new bearings are in order.

I would like to use the crank if possible but I want long term on this. What is acceptable sideplay and what else should I look for on it?

[C-LEIGH RACING]

Should be no side play between the crank & bearing on the flywheel side,
Both main bearings are press fit into the cases & crank is press fit into the flywheel side main bearing.

On the clutch side & using an oem Honda crank, the crank should be a slip fit into the main bearing.

If it is a Hot Rods or Wiseco aftermarket crank, they are machined different from the oem Honda cranks & are press fit into both main bearings.
All cranks are super hard surface in the main bearing area, so if you want the Hot Rods or Wiseco crank to be slip fit on the clutch side, the bearing race must be sized on the inside to allow it.
BDT Motorsports, has those main bearings in stock that are already machined on the inside for a slip fit.
Neil

[dtek01]

Luckily there is no crank side play but I was wondering about rod play. I can grab the rod and wiggle it a touch. What is acceptable for the rod play?

It is an OEM long rod 88'

Also does the counterbalance have a little wiggle play as well or supposed to be tight?

Thanks Neil!!

[C-LEIGH RACING]

The Honda OEM manual, has a rod wear limit listed. You could check that & see how much it is worn.
The problem would be who ever is getting the measurement if it is correct or not.

Theres an old school way that lot of old builders use to check the crank & rod wear & I use this way myself.
If you have the crank pulled out of the cases, hold the rod in your hand suspending it in the air & then take a rubber mallott & whop the rod on the end.
Takes a pretty good whop, but not hard enough to knock the crank out of your hand.
If the crank needs to be replaced or a new rod kit installed, there will be a ping like ring out of the crank when you whop on it with the mallott.
What is happening, when you strike the rod, it is taking up the worn clearance between the bearing & rod inner race surface & will produce a ping like ring.


Check this out, just put a new Hot Rods crank in my daughter 250R engine & before I installed it, I did the old school test on the old crank that came out & the new Hot Rods, both had a good ring to them, so thats telling me the new Hot Rods has just as much clearance in the bearing area as the old used crank.

Now the new Wiseco crank I got & just before sending it to Carlos to do his mod on it, did the old school test & was just a thud, no ring, so I know its tight in the bearing area.

Hot Rods might be machining in to much clearance into the big end on their rods.
Neil

[dtek01]

Intersting way to check! I will see what it sounds like.

[tex250r]

How does your main bearing look? You should be able to see a few of the needle bearings at a time without removing anything but the cylinder.

I just did a top end rebuild on mine. If I took the top of the rod and moved it side to side there was a little play. Granted its so much leverage a little might seem like a lot.

As far as up and down there was very very little movement, ( only could feel it couldnt see it) My main bearing look spotless. No pits, no flat spots, no discoloration. Mine looked new and I had a true mech look at it and he said it looked great so I didnt tear it down any further.

If you go to my thread about 1988 250r overhaul some nice gentle men posted a link to a free shop manual. Cant remember who and I dont know how to post a link.

Hope this helps
KO

[DnB_racing]

Originally posted by tex250r
I dont know how to post a link.

Hope this helps
KO just right click on short cut or link and select (copy short then paste on new page) http://www.mediafire.com/?kedw7x1dzmc83bl