Jump to content
Sign in to follow this  

Best Bore up kit for xr400

Recommended Posts

Hi all

Can someone recommend a complete bore up

Kit for a 1998 xr400.

Engine is down and power and needs new top end so I thought I might as well increase bore at the same time.

Can someone recommend kit and where to buy? I am in the uk but am happy to buy from Europe or us.

Cheers

Share this post


Link to post
Share on other sites

I was looking for the same answer a few weeks ago, done quite some research, there seems to be 2 safe ways to go: 426cc with 11.0:1 compression, or 435cc (usually called 440!) with 10.0:1 compression. With the former you can use the stock sleeve, you save some money there.

Piston: the best recommended by different racing shops was Wössner (Germany), then comes Wiseco (USA) and JE. Wössner is only a bit more expensive, I say go for it: http://forged-pistons.co.uk

Gasket set: use Cometic, I've got mine from: www.performanceunlimited.co.uk

Wait to have advices from others as well! :bonk:

PS: the top end is another story, but if they are in really good shape you don't really have to touch them. You can also leave the stock cam in.

Share this post


Link to post
Share on other sites

I feel that the cylinder liner is getting pretty thin @ 426. I've ridden XRs wtih 416 and 440 kits. The 440 has a bit more grunt down low but not much difference otherwise. The difference between stock and 10.5:1 416 is huge though.

Share this post


Link to post
Share on other sites
I feel that the cylinder liner is getting pretty thin @ 426.

Good point, I was thinking the same, but many 426 run on the stock sleeve, I haven't heard stories of them cracking. Also piston manufacturers advise resleeving only for 435cc, I think they would do otherwise if it would be risky. Boy I hope I'm right :bonk: time will tell :smirk:

Share this post


Link to post
Share on other sites
Good point, I was thinking the same, but many 426 run on the stock sleeve, I haven't heard stories of them cracking. Also piston manufacturers advise resleeving only for 435cc, I think they would do otherwise if it would be risky. Boy I hope I'm right :banana: time will tell :bonk:

I think that the results speak for themselves also. I've never heard of any problems so, no worries. :smirk:

Perc

Share this post


Link to post
Share on other sites

I did a 426 11:1 weisco piston, stage 2 hotcam, and cometic gasket set last winter. I bought everything on ebay. At the same time I port and polished the head myself and got a used FMF megamax pipe for it. I couldn't be happier with the amount of power I added. I can bring the front end up at 55mph in fourth gear with 16/42 gearing. With stock(15/45), or my dirt gearing (14/45) a fifth gear wheelie is easy to do.

It ran great with no problems all summer long. I ran premium gas the whole time. Just had one problem with a small bit of knocking while riding on sand dunes on a hot summer day, Switching to race gas fixed the problem.

Share this post


Link to post
Share on other sites

Shrk352, did you touch your clutch? Sometimes my clutch does slip, I'm still to find out why. Plates? Will measure. Springs? Will install +10% stronger Lucas. Oil? Running now on Motul 300V fullsynt, but will try 5100 semisynt.

Share this post


Link to post
Share on other sites

I put in new springs when I did it the upgrades. The clutch held out halfway through the summer then it started slipping and I replaced it all. First time I changed the clutch in the two years since I owned it, so I'm not sure how many miles it had on it, was probably about due for a new one anyways.

Share this post


Link to post
Share on other sites

Slipping solved with HD +10% EBC springs. Discs were all 3.00mm (service limit 2.69mm) after 12k dirt kms on the original clutch.

Share this post


Link to post
Share on other sites
Anyone ever thought of a "stroke down" to make the engine rev quicker??? just a thought:smirk:

for ex, a 375 short stroke quick rever!

No... this would go against the what the XR is known for... Torque!

The longer strokes are what makes the XR400's the torque monsters that we love.:smirk:

Perc

Share this post


Link to post
Share on other sites

Well... I don't want to say that it's overrated, but...

I rode two strokes for years when I was young and had quick reflexes. Now, let's just say I'm not so young and my reflexes are not so quick, so I just enjoy the grunt of my XR400. If I wanted quick horsepower, I would think about buying something else. What do you think ? :smirk:

Perc

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

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×