Project 1984 ATC 250R

[ianj454]

Hi guys and gals, I'm looking to get my 1984 250r sorted out into a reliable machine. Right now its running but not right.

I have to do a full bottom end rebuild due to slightly sloppy crank bearings. Anything I should look out for thats different on these machines?

It currently doesn't have a stock carb (37mm for some reason), but I have a stock carb and set of jets bought that came from a running bike. It has a brand new DG exhaust, and I am wondering how far I will need to jet for this? I live at sea level so should I start from 1984 stock and work from there?

Also I am looking for a set of used tank shrouds with no luck so far. I found these online, anyone have any experience with this site?
https://www.dcvmx.com/xcart/product....cat=662&page=1

Attached is a picture of the bike last summer, any help would be greatly appreciated!

[seth6025]

Hi the jetting I am not much help with and would like to know what other say because I am going to be jetting mine as well and I am at sea level. I have a 1983 so same bike pretty much. I would think the 37mm carb might be a bit big but maybe not. I do know the recommended upgrade for our bike is a 34mm Keihin. As for the tank shrouds I am looking at getting the same ones. I here they are nice but you do have to make some minor adjustments to make them fit.

[yaegerb]

Hi guys and gals, I'm looking to get my 1984 250r sorted out into a reliable machine. Right now its running but not right.

I have to do a full bottom end rebuild due to slightly sloppy crank bearings. Anything I should look out for thats different on these machines?

It currently doesn't have a stock carb (37mm for some reason), but I have a stock carb and set of jets bought that came from a running bike. It has a brand new DG exhaust, and I am wondering how far I will need to jet for this? I live at sea level so should I start from 1984 stock and work from there?

Also I am looking for a set of used tank shrouds with no luck so far. I found these online, anyone have any experience with this site?
https://www.dcvmx.com/xcart/product....cat=662&page=1

Attached is a picture of the bike last summer, any help would be greatly appreciated!

you sure the carb is not a 38MM keihin. A 37 is not a "normal" size.

[ianj454]

It definitely is a 37mm (see attached picture). If I went with a 34mm would i keep the jets the same as stock. I also found someone online said DG said to bump up 2 jets for the pipe and silencer. I am assuming this would only be for main or would this include pilot too?




EDIT: I am able to get the 34mm for my bike. Which carb is better for my set up and which is easier to get jets for?

[yaegerb]

It definitely is a 37mm (see attached picture). If I went with a 34mm would i keep the jets the same as stock. I also found someone online said DG said to bump up 2 jets for the pipe and silencer. I am assuming this would only be for main or would this include pilot too?




EDIT: I am able to get the 34mm for my bike. Which carb is better for my set up and which is easier to get jets for?

other than a DG exhaust what other modifications have been done to the engine?

1. does it have porting?
2. does it have aftermarket reeds (vforce or boyesen)?
3. do you know what the static compression is?
4. are you running an airbox with lid?

[ianj454]

1) I don't think it has any porting.
2) The new reeds I have coming in are boyssen
3) I haven't done a compression check yet, but it has a brand new piston I put in myself with maybe 2 hours on it.
4) I will be running with the air box lid on with a brnad new uni filter

The only thing unknown is if the cylinder was bored out or not. My guess is it was.

[yaegerb]

No need for the 37 then. Clean the stock carb extremely well and set it to the following specs. I assume it's a PE30

Float level: 20mm
Air screw: 1-1/2 turns out
Needle clip: 3rd from top
Main: 130
Pilot: 50

That should get you in the ballpark. Also I would highly advise a crank rebuild and pressure test before you even mess with the carb. Very likely that your seals need to be replaced.

[ianj454]

Thank you very much! The person I bought the carb off said it was a stock removed from a running bike.

I have brand new crank seals and brearings to go into the engine. I have a plan to build a leak down tester or is there a decent one around for a reasonable price?

[seth6025]

Not to hijack but would you not suggest the 34mm carb? Just curious because op is basically building the same bike as me and I have not ordered yet lol

[yaegerb]

You can go with a 34, but in my opinion it's not worth it if everything is basically stock except for reeds. You will loose a little velocity due to the larger bell housing on the carb so you may have to richen it up a bit for the bottom and mid.

[yaegerb]

Thank you very much! The person I bought the carb off said it was a stock removed from a running bike.

I have brand new crank seals and brearings to go into the engine. I have a plan to build a leak down tester or is there a decent one around for a reasonable price?

Do a search on pressure tester. I have a post somewhere concerning my set up for testing the motor.

[ianj454]

Made some progress today. when I took the sprocket off the crank I forgot about the balancer on the front of the motor. How do I align this when I put everything back together? Also I noticed a crack on the crank bearing housing, it don't extend all the way up to the bearing, so I'm not sure if its just from the casting.

[yaegerb]

Made some progress today. when I took the sprocket off the crank I forgot about the balancer on the front of the motor. How do I align this when I put everything back together? Also I noticed a crack on the crank bearing housing, it don't extend all the way up to the bearing, so I'm not sure if its just from the casting.

I can't really tell if that's a crack or casting flaw, need a clearer picture. If its a crack, you need to get that fixed.

1. Your crank has a tick mark on it and so does your crank idler gear. Ensure you place the proper gear (idler) on the crank and align the two tick marks.
2. Install the washer on the crank with "out" facing away from the motor and hand tighten the 10mm bolt
3. Your balancer shaft has a tick mark on it and so does the balancer gear. Ensure you place the proper gear (balancer) on the shaft, aligning the gear and shaft tick marks AND align the idler gear tick marks with the balancer gear.
4. Install the washer on the crank with "out" facing away from the motor and tighten the 10mm bolt
5. Both bolts are ~30ft lbs

[ianj454]

Thanks, I just seen the marks you were talking about. I have the cases split and the crank out now. I definitely needed new bearings both are rough. Im stuck now taking the bearings out. I tried them with a socket and but no dice. Just as always the torch tip is no where to be found, ill have to pick up a new one tomorrow. Any other suggestions for removing the main bearings.

Also my dumb ass picked up bearings last year for everything besides the crank. I took them out of the package today and found they are sealed. Is it fine to take the seal off, or should i order new unsealed ones?

[yaegerb]

Uhm....I would say those are the wrong bearings as crank bearings aren't sealed.....defeats the purpose of how the 2 stroke lubrication works.