'98 WR400 Rebuild options
Posted March 14, 2012 - 01:03 PM
The last shop claimed they were seeing 75% leak down and had a quote in excess of $3k to replace the head, cams, etc. If it's not the head, what could cause a leak that bad? I have reason to believe the shop was just trying to get more money out of me, but in case they were right, what could cause that?
The bike was "rebuilt" by the previous owner after it blew the motor. I can see some damage on the crank so I assume he reused the crank and just replaced the piston and cylinder. Will marring on the crank affect the rotational balance? Or would the motor blowing cause the crank to be untrue?
So best case scenario is that I have the cylinder checked and that it is ok, meaning the headgasket is the problem. Assuming the cylinder is out of round, I'll need to replace a bunch of stuff. What are my options? I want the most reliable setup, the bike was plenty fast for me, so squeezing every ounce of power out of it at the cost of reliability is not my goal. It is however a street legal bike and extra displacement would help me lug along at higher speeds. I plan on putting a 450 carb on there if things get sorted out, so the stock 98 carb isn't an issue either.
Is there some combination of 400, 426, and 450 parts that I can mix together to get this thing reliable and bulletproof? What all should I replace if I have to crack the cases(crank), or SHOULD I crack the cases to replace parts/bearings.
Finally, what should I expect as far as cost? This bike has had me so frustrated I was planning on parting it out and purchasing a 2-stroke trail bike to put around in the woods, but if I can get my wr in tip top condition for half the price, I'd rather do that.
Thank you for your time,
Posted March 14, 2012 - 07:11 PM
Posted March 17, 2012 - 04:00 AM
Posted March 17, 2012 - 10:30 AM
As far as rebuilding, it's looking pretty ridiculous as far as pricing. ~$400 for a cylinder and looking at around $1k for crank, cylinder, piston, and rings, not to mention all the bearings, gaskets, etc. It does look like the 426 parts are a hair cheaper though.
$1200 was my budget for a new bike, and I figure if rebuilding this one is more than half of that, it's getting parted out.
On that note, I'm taking the cylinder to a machine shop on Tuesday and having it checked for roundness, and that should help narrow things down.
Also, this bike starts first or second kick every time, whether it's been sitting or taken apart. Something isn't right. The plug, head, exhaust, etc were black black black. It was not sticky, but powdery, but the mechanic said oil was being burned and I trust his word.
Where do you guys get parts? Aftermarket?
Posted March 18, 2012 - 08:05 AM
Still looking for options here.
Posted March 19, 2012 - 10:04 AM
He also said that cylinder was 95mm? This is indicative of a 426 cylinder correct?
Any input fellas?
EDIT: he also said I could have it bored out and sleeved. Now I know that these are nikasil coated and that the general consensus is that resleeving is bad, but he said he would also use different rings for the piston as well that were designed to wear with a iron/steel sleeve.
Edited by nnamssorxela, March 19, 2012 - 10:12 AM.
Posted March 22, 2012 - 07:49 AM
Posted March 25, 2012 - 12:57 PM
Heat on crank, I'm under the impression this is to assemble the crank and rod?
The rod can wiggle side to side, and the piston can slide side to side on the pin. I'm under the impression that this is normal? Is there a reason I should take out and inspect the crank, or should I throw on a replated cylinder, new piston and rings and call it a day?
Posted March 25, 2012 - 03:45 PM
My list now is:
426 cylinder replate
426 piston and rings (do I need the pin and circlips too?)
05+ 450 carb
Do I need to check the crank, or can I assume it's good?
Any reason I should keep the 400 carb for breaking in? The shop said it was in good order but running a bit rich. Would this help with break in before I start tinkering with a 450 carb?
Posted March 25, 2012 - 05:03 PM
I think carb because you said backfire and sputters, many of the old carbs is just worn out. My own wasnt starting right, popping, sputtering, wouldnt idle etc. and an 08 carb made it pretty much a new bike. Be sure to get a 06 + carb, it has a leak jet, it makes the bike a lot more smooth. The leak jet does so that the acc pump is only activate if needed, where the old ones always just follow the slide.
When you order the newer carb you need the clutch lever bracket and all the cables, and remember to seal the old hotstart manifold.
Since you have everything a part i would check everything, get the manual to see all the tolerances, i think there is one for the roundness's too. If everything is ok, I would just go with new rings.
Do ALWAYS change the circlips if you had then out. As far as i know the 426 piston dont fit without a new rod, the diameter of the pin is different. See: http://www.thumperta...n-the-easy-way/
Posted March 26, 2012 - 04:19 AM
What is the clutch lever bracket?
Posted March 26, 2012 - 11:13 AM
I guess its called the clutch perch then with the newer carb you will have the hotstart up there..
Posted March 26, 2012 - 12:02 PM
Is the needle bearing on the crank? I was trying to avoid splitting the cases, but I suppose it would be silly not to? I'm worried by the time I get it all apart I'll need a new crank after all, as that seems to be my luck. I'm looking at ~$380 for a replated cylinder (if it needs one, see below), piston, rings, gaskets, etc, and ~800 when I throw the crank into the mix with it's 2 bearings.
I just got back from the machine shop and they said it was round, but that I was .003" over 95mm. Is the cylinder suppose to be exactly 95mm? The manual didn't say, only that the tolerance was .002". Is there supposed to be room for the rings, or is the piston a little smaller than 95mm to allow for the rings.
Posted March 26, 2012 - 04:25 PM
Pistons are a bit smaller in diameter, the limit is 0.1 mm. With that in mind you can easy measure if there is too much clearance.. If you are in doubt you can call wiseco for example to hear there min/max clearance..
The manual says that the round limit is 0.05 mm Read the manual carefully, the two of us will just get inches and mm mix up I think
Posted March 27, 2012 - 07:17 AM
There is a little slop at the bottom of the rod side to side, and I was told this is normal?
Posted March 27, 2012 - 02:41 PM
The rod needs freeplay from side to side, so yea thats normal. But up and down there shouldnt be much, about 0.03mm I'd say... If it feels like alot measure it, but it can be tricky to measure correct..
Posted April 06, 2012 - 09:14 AM
What is the proper way to break this in, in your opinions?
Posted April 06, 2012 - 02:16 PM