Jump to content
Sign in to follow this  

DR650(780) engine assembly questions, Newbie Needs some Help

Recommended Posts

Howdy...over the last couple of months Ive collected the pieces to put together a pretty killer motor, BUT ive never done anything like this before and i'm a little gun-shy. I only get one shot at this and don't want to grenade this motor.Im going to be installing ProCycles Big-valve head, 780 big bore kit, stage 2 cam and big ole 41mm FCR.. Ive torn down the motor all the way to the connecting rod and ive got some questions:

1) how do you get the jug to slide over the new piston without using a ring compressor?

2) how do you check the ring gap and how do you know you have squared the rings.

3) How do I figure out what head bolts go where??? I learned after I tore the motor down to send my head to ProCycle for the big valve exchange that i needed to keep track of which head bolt went where because the factory service manual is wrong. :smashpc:

4) who here has "clay'd the motor" to check for valve/piston clearance?? Shouldn't it just be okay?

Im sure i have more questions that will pop up but thanks for any input, i really appreciate it

J

Share this post


Link to post
Share on other sites

I've never built a motorcycle motor but I've built several circle track small block chevys and will give my input. I'm sure the expert will chime in.

1) Why don't you buy a ring compressor? They're cheap, unless there is some reason you can't get one in there?

2) To check ring gap install them into the jug bore and get some feeler gauges to check ring gap. Don't know what you mean by "squared" the rings? Maybe if you have to grind them to get the gap that you do it square?

3) Don't know but in small block chevys we buy new head bolts because they stretch when new. I've used old ones too without any catastrophic failure.

4) I've clayed motors. It adds some work and piece of mind. Just install on top of piston, assemble to spec, turn over several times, disassemble and check clay thickness to insure a valve won't smack a piston at high rpm.

I'm no expert but that is what I know of the subject pertaining to cars anyway :smashpc:

Share this post


Link to post
Share on other sites
I've never built a motorcycle motor but I've built several circle track small block chevys and will give my input. I'm sure the expert will chime in.

1) Why don't you buy a ring compressor? They're cheap, unless there is some reason you can't get one in there?

2) To check ring gap install them into the jug bore and get some feeler gauges to check ring gap. Don't know what you mean by "squared" the rings? Maybe if you have to grind them to get the gap that you do it square?

3) Don't know but in small block chevys we buy new head bolts because they stretch when new. I've used old ones too without any catastrophic failure.

4) I've clayed motors. It adds some work and piece of mind. Just install on top of piston, assemble to spec, turn over several times, disassemble and check clay thickness to insure a valve won't smack a piston at high rpm.

I'm no expert but that is what I know of the subject pertaining to cars anyway :smashpc:

Thanks for the reply Jake... The ring compressor wont work since ill be lowering the jug over the ring/piston and there isnt enough room to do it that way unless i try to makeshift some sort of ring compressor out of a hose clamp or something

my terms may be off with the "squaring the rings" what i meant is getting them in the cylinder straight..

Ill try the clay trick.. seems like a good idea..

Thanks again.

Share this post


Link to post
Share on other sites

Can you not arrange the crank so that the piston is up, so that you'll have more room for a ring compressor? As far as getting the rings in the bore square (I assume to check end gap) just measure all the way around with a machinist's ruler. Also make sure the ring gaps are staggered correctly, and make sure you get them on in the right direction. I'd think their would be instructions with the piston or rings on how to install the rings correctly.

Share this post


Link to post
Share on other sites

I am very interested in this swap. I too bought the 780 kit and stage 2 cam, the #190 cam but not the head.

Anyway we do dirt bikes and we did a big bore harley this past winter and we install the piston with a normal ring compressor FROM THE BOTTOM but leave enough of the piston handing out of the jug to allow the wrist pin to be slid into place and the clip installed.

One person holds the cylinder with the piston hanging out the bottom over the rod, you align the rod and slip the pin in, install the clip and slide the piston up the bore while lowering the cylinder.

this makes it easy to install the piston/rings in the cylinder on the bench.

As fo the piston to valve clearance they say there is plenty of clearance with the 780 kit and #190 cam.

You could also just add a shim between the valve and rocker arm and turn the motor over slowly by hand to see if it hits. Say a .050 shim after setting the valves on top of the valve and slowly , carefully turn the motor over to make sure everything clears.

To install the head and then clay the motor is alot of work as is installing checker springs and a dial gage.

I build race motors and we use checker springs but it is not nearly as easy with a motorcycle.

I have put a shim between the valve and rocker arm and did it that way

Share this post


Link to post
Share on other sites
compressor?

2) how do you check the ring gap and how do you know you have squared the rings.

J

The rings require file fitting to the cylinder. You put a ring in the finished bore and then using the piston push it down in the bore using the piston to make it square to the bore. YOu then use a feeler gage and check the gap. If too tight you use a ring filer to add more clearance.

Use the piston in the bore as a tool to square the ring in the bore.

Share this post


Link to post
Share on other sites
3) How do I figure out what head bolts go where??? I learned after I tore the motor down to send my head to ProCycle for the big valve exchange that i needed to keep track of which head bolt went where because the factory service manual is wrong. :smashpc:

J

I'm sure pro cycle would know the lengths of each bolt. Just email them and ask. Use a vernier to measure each one's length and put them in the proper spot.

If I knew nothing about which bolt went where I am sure I could figure it out by dropping each bolt in it's hole and seeing if there was enough bolt to engage the threads properly. You can eye ball if there is too much engagement or not enough. This is not the proper way to do it , ask and if you can't find the answer drop each head bolt in a hole and re arrange them until each seems to have the right amount of thread engagement.

Share this post


Link to post
Share on other sites
I am sure I could figure it out by dropping each bolt in it's hole and seeing if there was enough bolt to engage the threads properly. You can eye ball if there is too much engagement or not enough.

+1

Just drop them in the holes and look at how high the bolt head sits above its seat. If necessary move the bolts to different holes until the heights are equal.

Share this post


Link to post
Share on other sites

the two DR's I did didn't require a ring compressor. Just squeeze the rings together as you slide the cyl onto the piston slightly cocked to one side. At that point they should just slide on. Worst case you can wrap the rings with a piece of sheet metal or light sheet plastic and place a hose clamp around that to compress the rings.

Share this post


Link to post
Share on other sites

+1 what ProCycle and ram1000 said. When you 'square' the rings in the bore you simply slide them into the cylinder in the normal fashion that they sit, and you slide the piston down on top of them UP-SIDE-DOWN to push them slightly down with the crown of the piston ... so that they sit square to the bore. Do one at a time. Check the end gap with feeler gauges and file if necessary.

I had to 'clay' my motor with the 190 cam and the H/C piston because i had interference. I used the old head gasket after cleaning it when i assembled it to test the clearance as i was going to take it apart to take the clay out. A good question is if you use the new head gasket that came with the 780 kit to use with the clay to check the clearance, can you then re-use it for the final assembly even though it has been torqued already? ProCycle? Thanks!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...