New valve guides for my KZ900-iron or bronze?

Well, it looks like a valve job is in my Z's future. What are the advantages/disadvantages to using iron vs. bronze guides on a KZ900?

Bronze is used for many industrial bushings and bearings. But the people at the many and various motorcycle engine shops can tell you better than I can:

www.fastbygast.com
www.kzzone.com
www.z1enterprises.com
www.dynoman.net
www.redlinecycle.com
www.zpower.com.au

It may be different for some, but if the head was equipped with iron fromt he factory, and you plan to use the engine for street duty then stay with the iron guides. they don't gall like bronze will if you don't warm the engine up properly, and wear longer than bronze guides.

typical consensus in the hot rod car world is that iron guides are for street use with the big exceptions being the big inch monster motors that don't see light of day except for cruise nights and track time.

The difference in expense is not horrifyingly big, but bronze guides are a bit higher in price typically. You won't get the time with them that you will from iron.

Talk to the guys listed at the sites above and see what they say. Mostly it depends on application, but every engine builder has his opinion.....prepare a list of questions that you think are pertinent to the questions and answers you will get form them.

Skint

Thanks for the replies. I'm actually sending the head to one of the businesses that MFolks listed, and just want more knowledge. The original guides are brass. Sounds like iron is indeed the way to go.

According to Dave Marsden:
In the original Z1 cylinder head, the eight valves moved in bronze guides that were pressed into the head and secured by small circlips. These guides proved to be too soft for the job and were one of the few mistakes Kawasaki engineers made. They were later modified to a cast iron item.

Good Luck!

ive always liked iron guides myself but like you said it depends on who you ask B)i also prefer steel valves in most cases also ,maybe im just cheap!that should stir up a shit storm !:laugh:

on my own street engines that are going to see lots of street miles i tend to go with cast iron but on perfomance motors i use bronze the bronze guides are easir to drive in and easier to ream them out after they dont hold up as well to the wear and tear as cast. the cast guides can over time actually adhere to the cylinder head and cause problems driving them out[metal transfer ] that is why you see oversized bronze guides available aFTER market.

NOTE THIS!

You should not use the old KZ900 valves with later model KZ Cast Iron Guides.

In 79, they went with cast iron guides and changed the valves. You can use a new valve[79,80] with the old guides but don't use an old valve[73-78] with the new guides.

I like cast iron guides for longevity. Bronze guides in the early KZ heads were junk. However, replacing them with new bronze guides is fine. It's the honed clearance that makes or breaks the deal. I've installed lots of APE bronze guides and they work just fine.

Most times, KZ1000 heads with cast iron guides, the guides are still in good shape when they arrive for porting and valve jobs. It's not uncommon to remove the cast iron guides, port the head, shape and then reuse the cast iron guides.

Larry C

Eric, no advice, but perhaps a share of info. Old english twins had problems w/ seizing valves when run for prolonged periods.a common stop gap was to run bronze guides. In the day, replacement oversized valves, "Manley" comes to mind were a favorite, they were "stainless", and recommended bronze guides. My personal experiance is that iron guides wear well. In fact, even after experiancing "mushroom forrest"syndrome, my "77 kz1000 w/new valves fell into spec.G