Starting w/o Exhaust system on

Starting w/o Exhaust system on 20 Sep 2006 21:45 #78376

risccas Topic Author Offline User Posts: 19 Thank you received: 0	I just bought a 1974 Z1-900. It has the original exhaust w/ it but it's currently off the bike. Is it safe for the bike to try to start it with out the exhaust on it? Is it possible to damage the motor that way? Jason Attachments:
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 20 Sep 2006 22:51 #78386

Six9GS Offline User Posts: 54 Thank you received: 0	DUDE!!!! I have no idea. As long as you don't run it for hours without exhaust pipes, I kinda think it won't harm anything. But, I could be wrong. HOWEVER, DUDE That will sound LOUD!!!!! Oh Man I'd love to hear that!!!!! Rock On!!!
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 04:16 #78400

madderkaw Offline User Posts: 83 Thank you received: 8	I once started, and rode around a little, a CB750 without the exhaust. Really really loud, and flames came out of the exhaust holes. It was pretty cool.
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 05:17 #78410

The Gringo Offline User Â¡Usted no necesita otra motocicleta! Posts: 1770 Thank you received: 11	It would not be advisable, it is too easy for the cold outside air to get in there and bend a valve. Andy Akron, Ohio 80 Z-1 Classic-Sold 84 GPZ1100 79 KZ 1000 LTD 78 KZ 1000 A2 77 KZ 1000 LTD-Sold 76 KZ 900 The definition of a barn find 76 KZ 900-Sold gone to Denmark KZ 750 times 3, KZ 650 times 8 Sold 1 down to 7 KZ 550 times 2 80 440LTD-Sold 81 CSR 305-Sold 81 Yamaha XS650 Special
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 05:21 #78412

BSKZ650 Offline User Posts: 2064 Thank you received: 14	DO NOT RUN THE BIKE WITHOUT IT!!!, it will bend / burn valves!! 77 kz650, owned for over 25 years 77 ltd1000, current rider 76 kz900, just waiting 73 z1,, gonna restore this one piglet, leggero harley davidson SR, Ride captian, S.E.Texas Patriot Guard Riders.. AKA KawaBob
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 05:25 #78413

flht1997 Offline User Posts: 513 Thank you received: 2	i think if you just want to know if it will start, fine, run it for a few seconds and then shut it down. and how is cold air going to bend a valve? Matt Milwaukee, WI 75' KZ400, (5) 78' KZ400, 76' KZ 750, 78' KZ650 78'CB750F, 78' CB550K 89' BMW R100RT 05' H-D Electra Glide 06' KLR650 Do it right or don't bother doing it at all.
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 05:29 #78414

wiredgeorge Offline User Posts: 5310 Thank you received: 44	This is not a great idea. Cold air pulled into the combustion chamber (COLD AIR WILL BE PULLED IN) will hole a piston in very short order. Like I said, not a great idea to start the bike without the exhaust. wiredgeorge Motorcycle Carburetors Mico TX www.wgcarbs.com Too many bikes to list!
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 06:22 #78426

steell
Offline
User
Posts: 6850
Thank you received: 207

flht1997 wrote:

i think if you just want to know if it will start, fine, run it for a few seconds and then shut it down.
and how is cold air going to bend a valve?

Because it will not cool the valve equally.

A long time ago when I was 18 years old I worked for a metal fabrication shop, and my job there was to straighten rather large I-beams. This was accomplished by heating one side with a torch and throwing water on the other side. Since heat and room temp water can bend rather large I-beams (as in 36" across the web), I have no problem believing it can do the same thing on little valves (heat and room temp air).

I don't think running it for just a few seconds will get the valve hot enough to cause a problem though.

KD9JUR

Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 06:38 #78431

risccas Topic Author Offline User Posts: 19 Thank you received: 0	Yes, I'm just looking to start it for 5-10 seconds. Jason
	Please Log in or Create an account to join the conversation.

Starting w/o Exhaust system on 21 Sep 2006 07:20 #78439

flht1997
Offline
User
Posts: 513
Thank you received: 2

ok i agree cool air will be pulled in. but what temp exactly is the temp of the air coming in the intake side? i know the exhaust side is closed and the stem will not receive any cool air blast, but i feel that the mixture, while it will be affected, will not be signicatly leaned to cause engine damage when run for a short time.

Matt Milwaukee, WI
75' KZ400, (5) 78' KZ400, 76' KZ 750, 78' KZ650
78'CB750F, 78' CB550K
89' BMW R100RT
05' H-D Electra Glide
06' KLR650
Do it right or don't bother doing it at all.