View Full Version : modded minimoto keeps blowing reed valves

3rd December 2005, 14:53
Is anyone having reed blowing issues ??we seem keep blowing reed valves the PBU headstrong kit is so high compression that on the downstroke the reeds are trying to exit the engine via the carb

2 runs and the reeds are fucked. is anyone else popping the std metal reeds

today we fucked around with the fully tricked up bike for a bit and it shat itself - another set of reeds after 2 10 min runs

then we gave up on that and put the race pipe on a std day 2 that had the needle lifted up one notch, it actually went better than the modded one for about 10 mins then seemed to loose power. couldnt be fucked pulling it down to see what the problem was, dont think its reeds cause it still idles, when you open it up it wants to die now, im wondering if the fuel/oil is too lean, and its getting hot after a little bit and the extra drag on the piston is robbing it of powers? the mix is 40:1 using castrol r30 (not my pick but what my mate likes running) it has some caster in by the smell of it.

need to get some carbon or fibreglass reeds for the std block ...Beast can you help there ?

see you cunts later, its a nice day for a ride, pity ive had too many beers :doh:

White trash
8th December 2005, 21:02
Well us "cunts" reckon you've got the wrong kit on it. Try running two base gaskets. Some thing's obviously not right.

Did you change the crank?

Mine started first try, runs faultlessly and (now) has no issues.

The Beast
8th December 2005, 21:13
Yeah that's what you get for not buying from Xtreme aye Jimmy :msn-wink: :2thumbsup

Yeah I think we might have some carbon reeds for the standard reed block.
PM me

9th December 2005, 15:01
Cheers "Cunts" :bleh: :bleh: :bleh:

WT do you also have the PBU headstrong kit ? the crank and rod is standard, we are actually beginning to think the piston may be wrong as it has windows in it and they dont line up with anything, i think its meant for a 4 port barrel the barrel is a 2 port fked if i know

http://www.pocketbikesunlimited.com/49YELLOWJACKET.html - this is the kit, the barrel look different

Beast - we have made some fibreglass reeds, are yet to test, will get some CF ones off you if these are all shit
see you later

The Beast
9th December 2005, 15:10
WT has a kit, but its the Xtreme Power Machines equivalent to what you're talking about

Here it is:

9th December 2005, 16:42
Quite a bit different piston by the looks of it, this piston has two windows on in inlet side and two holes drilled either side of the Gudgeon pins on both sides...

what CC is that kit

The Beast
10th December 2005, 17:10
I see, yeah you can't actually see the window in the piston, but it is quite large. The kit is a definate 49cc, we have measured the barrell. Sorry I meant fibreglass reeds not carbon fibre. :doh:

10th December 2005, 20:57
Even with high crankcase compression, which it won't be especially if it has a crank anything like the one in the picture, the reeds shouldn't be a problem. The only time I've had problems with steel reeds is when there is something wrong with the reed valve cage or how it was assembled. Every time, I lost little 'chips' off the end of the reeds and they developed cracks running back along the length of the reed. Check to make sure the reed is fully and evenly supported when in the closed position and that it has some support in the fully open position.

The Beast
11th December 2005, 21:57
Yeah you don't want them too loose. You want them loose enough to open up with a little pressure but not so loose that they just flap around.

11th December 2005, 22:12
With the revs those things seem to pull you would need stiff petals and on the short side as well to get the resonant frequency up. Loose doesn't come into it. Try making some out of say 2L ice cream lid. It will only rev to about 1500rpm and won't accept throttle.

14th December 2005, 14:43
we gonna try the homemade fibreglass ones and see how they go, My mate tried a different carb (off a xr50) and it seems to be quite good, a lot more tuneable, high and low end mixture, bit boggy down low, but revs like a banshee

The Beast
14th December 2005, 15:38
What does it actually rev to?

14th December 2005, 18:38
fuck knows at this stage , havent got a rev counter, thats in the pipeline