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CRF 450 Engine rebuild


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I am currently in the process of tearing down the engine on my '07 CRF 450r. I am at the stage of taking apart the bottom end and plan on rebuilding everything from the bottom up. I have never taken apart a dirtbike before and am just going on the Clymer's manual that I have. Looking for a little help here and there and some pointers on potential bottle necks that I may run into. Any help or advice would be greatly appreciated!

First question. I want to clean everything off the disassembled parts. Suggestions? Is there any cleaners/solvents that I shouldn't use on certain parts? I currently have some engine degreaser, brake cleaner and carb cleaner. I read something about simply green but was thinking that might be more for cleaning the engine when all the plastic and electrical components could be an issue. I want the bike to shine when I'm done this rebuild!

Anyone have an tips here?

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You can use brake cleaner on the whole motor, even on the electrical stuff, it will not hurt it and is a great degreaser. Main tip I can give you is just make sure you have the proper tools. Flywheel puller, case splitter, press, torque wrenches and all that fun stuff.

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Ya I was considering taking a look on ebay or from a download site for that real service manual. The pics in my manual are ambiguous and it really doesn't explain how to do some of the trickier tasks in more than a couple words.

As for the flywheel puller, case splitter, spring tool and press, where would you suggest I pick up these tools? Are they dirtbike specific tools or can they be purchased at an automotive store?

As for the parts I am looking at buying, here is the list:

HOT RODS CRANK BEARINGS AND SEALS KIT

HOT RODS COMPLETE CRANK ASSEMBLY

ATHENA GASKET KIT - COMPLETE

WISECO PRO-LITE PISTON - STOCK BORE 12:1 COMPRESSION

Havent decided on any valve kits...suggestions? Is a camshaft something I should consider also at this point?

I want this to be a relatively inexpensive rebuild with reliable parts being the priority rather than performance. Bike has about 100 hours on the engine and the crankshaft failed so I'm doing it all more for a learning experience on the inner workings of the bike.

Once again, thanks for the replies and help! Hopefully a couple other mechanical noobs can benefit from some of my questions.

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the flywheel puller is dirtbike specific, but im not 100% sure about the other tools.

and I would recommend buying an OEM gasket kit versus that athena one.

I recommend installing stainless steel intake valves versus the IMO junk titanium ones. theyre a tad louder and heavier, which will take 1-2 HP off the top end, but theyre totally worth it because they are much tougher, and will last 2 or 3 times longer than the TI ones, and also require less shimming. because you will be losing power..maybe you should order a high comp piston to even it out? 13.5:1 should work.

I dont think your cam shaft will have to be replaced, but it might be a good idea to replace the cam bearing.

that sucks that the crank failed after only 100 hours... my bike has 150 hours on it and the crank seems to be good still, but I wouldnt be surprised if she went within the next 100 hours or so :'(

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good luck with your rebuild, roughly how many hours did u get out of a piston for your 07. How long do the bottom ends last? Not trying to hijack your thread but im thinking of picking up an 07 450 with three hours on it

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Is there a cost effective 13.5:1 piston? I think a jump from a $180 wiseco piston to $300 piston may not be worth it at this point....may be worth a slight hp loss.

ouch, I didnt realize the price difference was so much... kinda stupid IMO and I dont blame you for sticking to stock compression.

why are you choosing wiseco if youre staying stock compression? you can get an OEM piston thats stock compression for 96$.. that includes rings, wrist pin, circlips...you will NOT find cheaper than this: http://cgi.ebay.com/ebaymotors/Honda-OEM-Piston-Kit-2004-2008-CRF450R-CRF450-CRF-450_W0QQcmdZViewItemQQhashZitem45f1e4928cQQitemZ300411032204QQptZMotorcyclesQ5fPartsQ5fAccessories

dont know what you think of this brand... the oil ring looks kinda sketchy, but its a 13:1 http://cgi.ebay.com/ebaymotors/HONDA-CRF450R-CRF450-WISECO-PISTON-KIT-HIGH-COMP-13-1_W0QQcmdZViewItemQQhashZitem335b17ed70QQitemZ220571626864QQptZMotorcyclesQ5fPartsQ5fAccessories

and here, I found you a wiseco piston for 170$. not quite 13.5:1, its only 13:1 but still pretty damn close... http://cgi.ebay.com/ebaymotors/Honda-CRF450-02-07-13-1-Wiseco-piston_W0QQcmdZViewItemQQhashZitem45eef83e67QQitemZ300361989735QQptZMotorcyclesQ5fPartsQ5fAccessories

13.5:1 JE piston for 180$: http://cgi.ebay.com/ebaymotors/JE-Piston-Ring-13-5-1-CRF450R-CRF450X-CRF450-CRF-450-R_W0QQcmdZViewItemQQhashZitem2eaa2279a9QQitemZ200422881705QQptZMotorcyclesQ5fPartsQ5fAccessories

ps: I would recommend buying all your parts off ebay... exact same stuff you would get anywhere else, but for a fraction of the price. some people like to pay high $$ and buy it from a big name site, or a stealership, but ive bought 1000s of dollars worth of parts off ebay with no problems at all, and saved myself 1000s of dollars in the process.. its up to you!

I just replaced my head with a brand new one with SS intake valves ready to be bolted on, a new cylinder, new piston + rings + gaskets, everything, and it cost me 950$ total.. so a full engine rebuild (new head, piston, cylinder, crank) can be done for about 1200$ if you shop smart... or $2000+ if you buy the same parts from a stealership or online distributor.

hotrod crankshaft, everything ready to go.. 250$ total after shipping: http://cgi.ebay.ca/Hot-Rods-Crank-Honda-CRF450R-crankshaft-CRF-450R-450_W0QQitemZ160408562803QQcmdZViewItemQQptZMotors_ATV_Parts_Accessories?hash=item2559186c73

complete gasket kit, 80$ total: http://cgi.ebay.com/ebaymotors/COMPLETE-GASKET-KIT-HONDA-CRF450R-CRF-450-2007-2008_W0QQcmdZViewItemQQhashZitem2eac1f1aacQQitemZ200456215212QQptZMotorcyclesQ5fPartsQ5fAccessories

OEM cylinder: 230$ total: http://cgi.ebay.com/ebaymotors/Honda-OEM-Cylinder-2004-2008-CRF450R-CRF450-CRF-450-NEW_W0QQcmdZViewItemQQhashZitem53dffcdb96QQitemZ360240176022QQptZMotorcyclesQ5fPartsQ5fAccessories

so, IF you decide to buy all the parts I just listed, new piston, crank, cylinder, gaskets, bearings, everything except your head + valves and stuff, your total would be 740$ total.. plus another 200-300$ to get your head rebuilt with SS intakes, plus the special tools that are probably 100$ total, and you can rebuild your whole engine for under 1200$.. not too bad.

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I can still see the crosshatching, however there is significant wear (I felt it with my finger) on two opposing walls.

Next question. Is a specific clutch tool necessary when removing the main bolt? Is there any simple way to rig something up?

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I can still see the crosshatching, however there is significant wear (I felt it with my finger) on two opposing walls.

Next question. Is a specific clutch tool necessary when removing the main bolt? Is there any simple way to rig something up?

Ive had good luck using a vice grip on the inner hub with small pieces of wood padding the jaws of the vice grip. The vice grip i use is big enough to stick up between the fingers of the clutch basket and then I just wedge the drive gear and back the nut off. Its simpler than it sounds.

When you do a piston change, cylinder needs to be honed. When you say you can feel the wear, its a problem usually. You shouldn't be able to feel anything in the bore at all.

100 hours is the absolute max you should run. A good maintenance practice would be 50 on the piston and a 100 on the crank max if your racing the thing. The cranks are cheap enough to just replace.

There are lots of much less expensive pistons out there. I dont know where you found one for 300 bucks, unless its a procircuit piston. Sometime I think they pay retail for stuff and then mark it up 100% with the Pro-Circus label on it.

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yah shawn_mc is right on with the clutch, thats the way i usually do it to (If I dont have the holder with me anyway) Yah if you can feel the wear then It needs to be honed. Problem is alot of times those nikasil cylinders cant be honed and just need to be replaced. Just depends. take it to a bike shop or even a machine shop who works on bikes regularly and have them look at it.

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I just did the same rebuild. Are you replacing the 4 trans bearings? You should definitely replace the balancer shaft bearings and seals.

Did you buy the complete gasket kit? I'm curious what's in it, since topend gasket kit plus center, left, and right crankcase gasket is around $90.

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Im just waiting for some tools (Casesplitter, flywheel puller, etc) before I finish the bottom of the teardown. I have not made the final purchase of all the parts and was gonna ask for some more recommendations when I get to that point. Someone recommended purchasing the OEM gaskets, Is it possible to get this complete kit with all the seals? Anyone have a cost effective recommendation once again?

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Case-splitters are not needed. If cases don't open easily with bare hands and maybe a light rubber mallet tap you probably missed a bolt (happened to me). Definitely buy the flywheel puller.

I'm curious what's in the "A" and "B" OEM gasket kits as well, it's not too clear on the parts diagram. I already had a Cometic topend gasket kit and bought the 3 case gaskets OEM. I also replaced the seals at clutch, shift lever, and counter-shaft sprocket.

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gasket kit a:

GASKET, CYLINDER 12191-MEB-671 $7.93

GASKET, CYL HD 12251-MEB-671 $22.62

GASKET, HEAD COVER 12391-MEB-670 $12.82

GASKET 14560-MEN-671 $4.44

GASKET, EX. PIPE 18291-MEB-670 $3.64

GASKET, MUFFLER 18392-MEB-670 $9.69

RUBBER, SETTING 90543-MV9-670 $3.65

WASHER O-RING KIT A 06114-MEN-670 $5.04

SEAL, RING 12226-MEB-670 $2.29

WASHER (6MM) 90442-397-000 $1.33

O-RING (19X3) 91312-KE7-003 $1.75

A seems pretty much all top end stuff, and B seems to be all bottom end stuff. pretty simple to figure out whats in A just by reading the names I posted, everything else is part of B which might not be too easy as ive never been inside the bottom end.. yet.

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What is the difference between the OEM gasket kits and the aftermarket kits? I have found aftermarket kits that include all the seals and it would be a lot more convenient, however, I dont want to scrimp on quality. Also I was reading through another thread and the guy was using a loctite liquid gasket or something. Does anyone have any thoughts or opinions on this?

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