Planet Minis

thermos · 09-04-2008, 05:00 PM

Well I threw on an 88cc Kit (cylinder& piston)from Beatrice Cycles. I also installed a 20mm Mikuni Carb. Stock head. I got a handful of rides on it and it ran pretty good. Well now it has a bent exhaust valve. Will I continue to bend valves with this setup? Am I wasting my money with replacing the valve or should I spend the money on the bigger head? I have a 4 month old daughter so budget spending is a must.

Thermos

fiddyonefiddy · 09-04-2008, 05:32 PM

you need to find out why it bent the valve b4 you start rebuilding.
why did it bend the valve is the first question you need to be asking.
how do you know the exhaust valve is bent?

thermos · 09-04-2008, 05:52 PM

Because it wont seat and I pulled it and it is bent. Not sure why it bent. Maybe from a bad adjustment? Not real sure. That is all that I did from the time it was running to the time that it lost all compression. Intake valve seems to be seated OK.

Thermos

firepower354 · 09-04-2008, 06:17 PM

Sounds like the timing is off, either through installation error or camchain stretch.

thermos · 09-04-2008, 06:22 PM

camchain stretch

What would cause that?

firepower354 · 09-04-2008, 06:24 PM

Honda uses a pretty lightweight chain. If there's much time on it, it's stretched. I wouldn't rule out assembly, though...

fiddyonefiddy · 09-04-2008, 06:27 PM

and check the cam chain adjuster
if you already got it apart you cant check your cam timing to see if it was off.
that is what bends valves cam timing is off .but you said you rode it for a while and then
it bent it. so that doesnt add up. if the cam timming was that far off it woulda bent it immediately. not after a few rides. so somethins wacky there, somethin broke.

thermos · 09-04-2008, 06:33 PM

So has anyone had any problem with this cylinder and piston (DrATV 8

on a stock head? The bike is just for trailriding. I will take the engine to my motor dude and he will tell me what is up.

Thermos

fiddyonefiddy · 09-04-2008, 07:38 PM

i havent heard of any

edmonster · 09-04-2008, 08:50 PM

timings off??? valves not adjusted right???

highho04 · 09-04-2008, 09:04 PM

My buddy has this same prob with his TB 88 RH. and we got prob bout 2 hours of ride time on it before the motor died from a bent valve, the timing was off by one tooth. Did your setup run good? or was it hard to adjust?

mavbike · 09-05-2008, 02:47 AM

Stock head (port and valve size) is holding you back. For the price, look at the DRATV head. It comes with Honda valves, heavier springs, and performance cam, already installed. The price is hard to beat.

Whatever you use, when you put the motor back together, double check all clearances. After assembly, check timing, turn the motor by hand and check timing again. The valve should not have bent unless timing was off or you floated the valves (easy to do with old well used stock springs).

fiddyonefiddy · 09-05-2008, 11:05 AM

my valve springs are from 1972 never had a problem with them floating.

09-04-2008, 05:00 PM	#1 (permalink)
thermos PM Newbie Join Date: Jan 2008 Posts: 7	CRF50 bent valve Well I threw on an 88cc Kit (cylinder& piston)from Beatrice Cycles. I also installed a 20mm Mikuni Carb. Stock head. I got a handful of rides on it and it ran pretty good. Well now it has a bent exhaust valve. Will I continue to bend valves with this setup? Am I wasting my money with replacing the valve or should I spend the money on the bigger head? I have a 4 month old daughter so budget spending is a must. Thermos

09-04-2008, 05:32 PM	#2 (permalink)
fiddyonefiddy 2nd Gear Member Join Date: Dec 2004 Location: Dallas Posts: 320	Re: CRF50 bent valve you need to find out why it bent the valve b4 you start rebuilding. why did it bend the valve is the first question you need to be asking. how do you know the exhaust valve is bent?

09-04-2008, 05:52 PM	#3 (permalink)
thermos PM Newbie Join Date: Jan 2008 Posts: 7	Re: CRF50 bent valve Because it wont seat and I pulled it and it is bent. Not sure why it bent. Maybe from a bad adjustment? Not real sure. That is all that I did from the time it was running to the time that it lost all compression. Intake valve seems to be seated OK. Thermos

09-04-2008, 06:17 PM	#4 (permalink)
firepower354 3rd Gear Member Join Date: Oct 2006 Location: Flint MI Posts: 6,266	Re: CRF50 bent valve Sounds like the timing is off, either through installation error or camchain stretch.

09-04-2008, 06:22 PM	#5 (permalink)
thermos PM Newbie Join Date: Jan 2008 Posts: 7	Re: CRF50 bent valve camchain stretch What would cause that?

09-04-2008, 06:24 PM	#6 (permalink)
firepower354 3rd Gear Member Join Date: Oct 2006 Location: Flint MI Posts: 6,266	Re: CRF50 bent valve Honda uses a pretty lightweight chain. If there's much time on it, it's stretched. I wouldn't rule out assembly, though...

09-04-2008, 06:27 PM	#7 (permalink)
fiddyonefiddy 2nd Gear Member Join Date: Dec 2004 Location: Dallas Posts: 320	Re: CRF50 bent valve and check the cam chain adjuster if you already got it apart you cant check your cam timing to see if it was off. that is what bends valves cam timing is off .but you said you rode it for a while and then it bent it. so that doesnt add up. if the cam timming was that far off it woulda bent it immediately. not after a few rides. so somethins wacky there, somethin broke.

09-04-2008, 06:33 PM	#8 (permalink)
thermos PM Newbie Join Date: Jan 2008 Posts: 7	Re: CRF50 bent valve So has anyone had any problem with this cylinder and piston (DrATV 8on a stock head? The bike is just for trailriding. I will take the engine to my motor dude and he will tell me what is up. Thermos

09-04-2008, 07:38 PM	#9 (permalink)
fiddyonefiddy 2nd Gear Member Join Date: Dec 2004 Location: Dallas Posts: 320	Re: CRF50 bent valve i havent heard of any

09-04-2008, 08:50 PM	#10 (permalink)
edmonster 1st Gear Member Join Date: May 2008 Location: Ely, Minnesota Posts: 125	Re: CRF50 bent valve timings off??? valves not adjusted right???

09-04-2008, 09:04 PM	#11 (permalink)
highho04 2nd Gear Member Join Date: Dec 2007 Location: Kansas City, MO or Pleasent Hill, MO Posts: 732	Re: CRF50 bent valve My buddy has this same prob with his TB 88 RH. and we got prob bout 2 hours of ride time on it before the motor died from a bent valve, the timing was off by one tooth. Did your setup run good? or was it hard to adjust?

09-05-2008, 02:47 AM	#12 (permalink)
mavbike PM Newbie Join Date: Aug 2008 Location: Shreveport Posts: 24	Re: CRF50 bent valve Stock head (port and valve size) is holding you back. For the price, look at the DRATV head. It comes with Honda valves, heavier springs, and performance cam, already installed. The price is hard to beat. Whatever you use, when you put the motor back together, double check all clearances. After assembly, check timing, turn the motor by hand and check timing again. The valve should not have bent unless timing was off or you floated the valves (easy to do with old well used stock springs).

09-05-2008, 11:05 AM	#13 (permalink)
fiddyonefiddy 2nd Gear Member Join Date: Dec 2004 Location: Dallas Posts: 320	Re: CRF50 bent valve my valve springs are from 1972 never had a problem with them floating.

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