Performing a 1250cc conversion on my Sportster next week

[Guest sling]

Just throwing this out there if anyone happened to be interested. Back in March I purchased an 06 883C with the sheer intent of converting it to a 1250cc. This isnt my first rodeo doing an engine conversion on a Sportster but it is my first time doing a conversion with NRHS products. NRHS uses Axtell cylinders with Wiseco pistons. They're also a proponent of Cosmetic gaskets which, in my opinion, are the best money can buy.

I never went with an NRHS 1250 kit in the past due to the fact that they were using less than desireable oil rings for the pistons and oil consumption was a huge issue. (Try, a quart every 500 miles ) This problem has been fixed now for about a year.

In the past 883 > 1200cc conversions that i've performed most of the engines suffered from detonation in the chamber due to the different timing and curve from the stock 883 ignition. This is (usually) remedied by going with a programmable ignition such as the Twin Tec 88A (TC88A), Screamin' Eagle Race Ignition, or even just the plain jane non programmable Screamin' Eagle ignition. Running colder plugs and high octane gas remedies the issue as well.

I can periodically update the article as i go along with information and pictures if anyone is interested in the process. This is my first write up on the subject so i may scant on some details. If you have any questions about the conversion i'd be more than happy to answer them for you.

[Bigiron]

Although I would never undertake such a task, I am envious of those who possess the ability to do so. I would like to read of your progress on this project.

[nightrunner]

wow, should be amazing when you get done. pics please!

[Guest Arko]

I only understand what you are doing in theory. Zip for mechanical ability myself, but I love bikes, so I'd like to see updates.

Good luck!

[revmike]

Let us know how this is going. I have a 2001 883 that I have been thinking about converting. I have some of the parts, 2004 heads, SE cams, S&S rocker arms and Mikuni carb.

[Guest sling]

I'll post updates as soon as i get my parts in and start working on the project. Shouldnt take more than 6 or 7 hours to piece everything together. Its fairly straight forward.

Let us know how this is going. I have a 2001 883 that I have been thinking about converting. I have some of the parts, 2004 heads, SE cams, S&S rocker arms and Mikuni carb.

Revmike, for the price you cant beat it. The most economical bang for the buck method is to have either HD or a speed shop (preferable) bore your cylinders out to 1200 dimensions. Just make sure whatever shop you choose to do this with uses torque plates when they bore.

HD's cylinders can be bored to a max of 1212cc safely. There are a few places that are ballsy enough to do it. Either way you go you will be immensely happy with the huge power increase.

If you go with cams on your 01 make sure you use those 2004 heads (im assuming their 1200 heads?) Your stock 883 heads arent going to have enough flow to justify adding cams. You could however send them off to a shop for headwork.

What kind of cams do you have? SE 551, 497, or 536's? Note that if you move to higher lift cams you may need to shim and\or replace to different valve springs.

The Mikuni carb is a great carb. Very very tunable. HD actually has a heck of a stock carb. It can easily support up to 100 hp when tuned correctly.

Also, im sure your aware, but when you convert your solid mount motor into a larger fire breathing beast it will vibrate way more. If you thought that was even possible....

[revmike]

Thought about getting the cylinders bored out, even bought an extra set of 883 cylinders off ebay, but I think I will get a set of iron lined aluminum cylinders. The heads are for a 1200. I got the SE 575 cams. Yes I have read about the vibration

[Guest sling]

I stretched this project over two days. Friday involved stripping everything down in the following order: Seat, air filter, carb, gas tank, exhaust, manifold. Once these parts were off you have clear access to the top end. I didnt take any pictures of taking those parts off because it is incredibly straight forward. Also, i found out that all of my rechargable batteries were dead on day one... so i didnt get many pictures.

*** Please note that the pictures with arrows on them i stole from a friend of mine on a previous build. My camera didnt work day one so...

So we begin.

1. Once you're ready to start working on the top end you will need to detach the stabilizer (rubber mount) that is attached to a bracket.. attached to the head.

The stabilizer takes a T-45 torx and the two nuts on the plate are 5\8. You only have to remove the torx nut on the right side of the bike... its incredibly difficult to get to the other one with a socket and unnecessary to remove.

2. Once these parts are removed you have access to the rocker box covers. Very straight forward. There are four 3\16 allen bolts on each rocker. Remove these and remove the cover. Note: Each allen bolt has a smaller fibrous gasket around the base of it. Remove these.

3. There are two rubber gaskets on the rocker box. One is a rectangular gasket in the center and the other is around the whole box. You will need to remove the breather valves for the crankcase breathers in order to continue. This will also allow you to get the large gasket off without it potentially going everywhere. (It happens) Take note which breather goes to which rocker. Black is front , brown is rear.

4. This is immensely important. You must close your valves before going forward. Do this to each rocker as you take them off. Pop the bike into fifth gear and turn the rear wheel until you close the valves. Doing this takes the pressure off the lifters. If you do not close your valves you can break a pushrod or any other of various crap. Do it.

5. Once valves are closed take out the two 3\16 allens on the outside of the rocker box.

6. Take off the three 7\16 bolts inside the rocker box.

7. Finally, Take these 4 bolts out in 1/4 -1/2 turn increments using a cross pattern. You will know when they are free and are able to take them out by hand. This uses a 1\2 socket. Pull off the rocker box and remove the metal gasket under it.

8. Take out your push rods and keep track of which one goes to which cylinder. They are marked Orange and White.

Rear Cylinder - Intake = Orange Exhaust = White

Front Cylinder - Intake = White Exhaust = Orange

If they arent marked or its rubbed off just keep track of them.

The intake pushrod is always longer than the exhaust.

9. The head. Have a breaker bar and a 12 point 1\2 inch socket ready. Depending on how old you engine is will usually determine how hard these suckers are to get off. You must take these bolts off in the following order. Turn the bolts in 1\4 inch increments. Failure to do this can warp the head.. after that i guarantee you will never get a good seal again.

Red

Blue

Pink

Green

Repeat the same with the rear

Once the heads are off there are two o-rings in the push rod holes. Remove them and go ahead and replace them with new ones from your gasket it. They're easy to forget about. No need to put everything back together and leak everywhere out of your tubes.

Also dont forget to remove the head gasket that is either still on the bottom of the head or on the top of the cylinder.

10. You dont have to remove the push rod tubes unless you want to. If you do make sure you replace the rubber o-ring in the tappet cover where they seat. Make sure you put them in straight or they will pinch resulting in an oil leak.

11. Once the heads are off you can pull the cylinders off.. but wait right there fido. Slowly pull the cylinder up about half way before clearing the piston and stuff a lot of shop towels into the crank case hole. You dont want anything falling in there, including possibly a broken oil ring on the piston (dont ask me how i know), because you'll be screwed. Once there is no possible way whatsoever for anything to get into the crankcase lift the cylinder off the case and place it somewhere. Take the base gasket off of the bottom while your at it.

And with towels in the crank case...

12. Now for the pistons. Take a small flathead screwdriver and insert it into the recess on the piston to pop out the 'C' clip holding the wrist pin in. It is very springy and will fly out. Use safety goggles if you need to.

Pop the spring out from the left side of the bike if you left the push rod tubes in. Once the pin is out push the wrist pin out and take off the piston. Note: Your pistons will have a layer of carbon on the tops. Its normally... especially with the amount of corn juice in our gas these days.

13. Follow the instructions with your piston rings in order to gap them. This very important. Improper gapping will lead to oil consumption. Bad.

Fit the rings to the piston according to your instructions.

** Side note. If you order from NRHS it is very much worth the $70 something to have them gap the rings and fit the pistons into the cylinders for you. I hate gapping and hate ring compressors so i'd highly recommend it.

14. Pin your pistons onto the crank arms. Make sure the C clip is on there snug. Its best to place one c clip on one side of the piston before attaching it to the arm.

15. Place a new base gasket onto the crank case.

16. Use a ring compressor to compress your rings and slowly guide the cylinder onto the stud and down the piston.

17. Place a new head gasket down. NOTE: If you are using a harley gasket kit make sure you place new o-rings on the oil receptor ports going through the clyinder. The two ports are the two holes that dont have dowels through them. IF you are using a Cosmetic EST gasket set... DO NOT use o rings on the oil ports. You will leak.

18. Torque the head onto the new cylinder using the same sequence that you used to take the heads off. Torque to the following specs.

In sequence tighten all bolts to 9 ft lbs. Then in sequence to 14 ft lbs.

Then in sequence 22 ft lbs. Then again in sequence to 35 ft lbs. Finally, in sequence again set the final torque to all head bolts to 42 ft lbs.

19. That is pretty much the gist of it. It would be redundant of my to show assembly... just follow your service manual and make sure you replace old gaskets with new.

20. Once everything is back together make sure the spark plugs are out and new oil is in. Put the bike in fifth gear and roll the rear wheel to make sure your pistons DO NOT crash into your heads. Keep your finger off the damn starter. Once you are sure that everything is fine. Cycle the engine with the starter without the plugs. You should feel air coming from the spark plug holes.

21. Heat cycles are important. Put the plugs in and start her up. Let the bike run for one minute and turn it off. Let cool completely. A fan helps in this. Repeat the cycling by allowing the bike run in 2, 3, and 4 minute intervals cooling completely in between. Finally, take the bike for a 20 mile ride. Come back and cool completely. Your heat cycle is complete.

Be easy on the bike for the next 500 miles and keep RPM's below 3200.

***End Notes*** Use non synthetic oil for 500 miles to promote breaking in and wear. Change to synthetic after 500 miles if you wish.

Make sure after break in you dyno your bike. No need to spend thousands on your engine and not squeeze all of the HP from the thing just because you didnt want to spend the $200 or so to dyno it.

I'm running a 42 slow jet and 180 main with the air\fuel screw out 2 1\2 turns for the carb. EFI will require adjustment as well.

I'm also using a Twin Tech (TC88A) ignition to prevent detonation. Detonation will destroy your engine.

Initial timing is set to 1

Advanced slope is on 3

My speedometer is +5 mph off as expected. Will have this adjusted during dyno.

*** If you have any questions feel free to email me or respond the the thread.

End Result... It WAS an 883... my exhaust got quieter though.... so its time for those 2.5 " baffles i've been wanting.

http://s4.photobucket.com/albums/y137/parisgrim/?action=view&current=DSCN7364.flv

Edited August 23, 2009 by sling