250-500cc WR300 Intake Manifold replacement ?

Old oem stock not stored correctly perhaps? Both my bikes have superficial scale type cracks. Thick rubber though! Had one replaced under warranty on 300 when near new as was lifting near a bolt head.

Both airboots have some small superficial cracks too but just whacked a bit of silicone over 'em-good as gold!

My 2013 WR125 boot was cracked after a couple of hours- i bought it brand new- replaced it twice in 2 years...
i think its a quality problem- never had a broke intake boot on any of my YZs

I just hope the Honda CR 250 boot will be a long term solution for these problems

I'll let you know as I will try to fit the Honda CR250 '99 this same week. Didn't have time to do it before, but tomorrow should be my last ride on that old boot. I do not trust them much... to be honest, I will go to the garage right now and apply some joint silicone just to be sure I have no air leak tomorrow.

Regards.

Thanks, that give me confidence. The Honda boots are way better, this 99 boot I bought has no cracks whatsoever. and it's a 18 years old part !

In reading these posts, I'm wondering if ethanol in the fuel may be to blame. Alcohol is very hard on rubber and plastic. I'm fortunate to have 91 octane ethanol free premium pump gas available in Missouri.
Just a thought....

Good thinkin' but I haven't ever run ethanol fuel in mine and I'm on my 3rd carb boot.

No ethanol here either & mine cracked too. I always thought it was from degreaser/cleaning products drying them out

I have heard (but have no direct experience) that ozone created by electric motors in the garage (furnace fans, dryers, vent fans, welders and so on) can degraded rubber parts.

More good thinking, but I don't have a garage

Had a look for Honda CR250 boot, but no new ones found yet. Looks like they should work. Freakin' ebay robbers want more for a used one than the price of new! Look forward to hearing how it fits. My 300 is the only bike this has ever happened to for me. 165 still has the original part.
I see Husky 2008 part is available, so probably try that next.

I m sure i ll help them degrading faster- but why do all carb boots from my yamahas last so much longer? never had to replace any of them (i have 2x 05yz125 and 1x 06yz250)

I'm using normal 95 octane pump fuel, here in Spain that is 'E5' so it has a max. of 5% alcohol.
I would blame it more on the degreaser stuff I use sometimes, I already use it diluted and for very short time, found no other way of getting that dirt off. White painted frames are a mess to clean well

I think I need to buy longer bolts first as I will try to use the VForce4 reeds and I'll use a spacer. Maybe next week I'll try this...

Regards.

Well, yesterday I was playing around with the Honda boot, the angle is quite a bit different:




I was able to force the carb in but there is some force on the boot, I loosened the bolts so it become more obvious:


It's possible to force it in but I don't think the boot will hold up for long, it's an 18 years old part I got second hand and during the assembly I already noticed some tiny cracks on the inside of the angle:

Did you also experience the same ? Maybe there are different versions of the Honda boots and some have a better angle ?

I think I will try it, if it will not hold up I will probably fab my own solid boot out of aluminum using a rubber joint as the GASGAS do. In fact, the GASGAS intake manifold would be an option but the angle seem to be even bigger, it's most likely needed to trim&weld the part to make it fit.

Cheers.

I purchased one from these guys about five or six years ago. Good quality not cheap though
http://hotfootmoto.net/store/product.php?productid=18557&cat=260&bestseller=Y

Well I did already have an air leak as it seems, I was noticing that the idle was a little higher than normal, let's see:




The typical crack on the upper side and the 'rubber' is pretty swollen up, that may indeed be related to the ethanol in our E5 gas...


There was already a channel to the outside world



For now I installed one of my older boots that were in better shape than this one, waiting to get a new gasket to try that Honda boot + the vforce 4 reeds.

Cheers.

Sorry to repeat my question but I am concerned about the non-perfect angle the Honda boot is giving me...

Did you also experience the same ? Maybe there are different versions of the Honda boots and some have a better angle ?

What year and model of Honda boot do you have ?

It's from a 99 cr250. Now that I have it I'll just try to fit it, let's if it hold up under stress :-/

Well? Did it hold up OK? Inquiring minds want to know!

:-)