high-altitude jets for '79 KZ1000ST w/PODS?

Hi,

I've tried using the search function for jet sizes relating to a '79 KZ1000ST at high altitude w/PODS but was unable to find any such thread.

My plugs are carbon-fouled and the factory jets have not been replaced since the aftermarket PODS were installed. What size jets would you recommend for high-altitude riding in Santa Fe, NM at approximately 7,000 feet above sea-level?

And also, anything else to keep in mind relating to high-altitude riding I should know? Doesn't the octane requirement go down to 85-86 at high-altitude?

Thanks. kzrider is my favorite site on the web!

1979 KZ1000ST
12,XXX original miles
PODS, e3 spark plugs

everything else on the bike is stock

Post edited by: onanysunday, at: 2007/10/01 16:55

What are e3 spark plugs? I would use NGK B8ES spark plugs as the heat range is correct and they are recommended in any factory service manual.

How do you know you have the stock jets? Have you removed them to check? With stock jets and pods, your jetting shouldn't be rich to where the plugs are carbon-fouled. Did the plugs carbon foul prior to adding the pod filters?

If you are using stock KZ1000E1 VM28SS carbs with pods, then you should be using #15 pilot jets, and #97.5 main jets and clip the 5CN17 jet needles to the 2nd slot. I suspect the stock jetting with pods shouldn't foul the plugs and you may have some other issue contributing to the plugs fouling.

Have you looked at the "Coil Repowering" tip on our website under "wg's Tech Stuff Index"? Also look at the "Valve Clearances" tech tip... both of these issues contribute to incomplete combustion (fouled plugs). Last, I am not sure how octane/gas is effected by altitude. You can probably do a web search but I suspect regular gas, whatever the octane , is about right as your bike has low compression and doesn't require the expensive stuff.

I just purchased the bike a month ago and haven't disassembled the carbs yet. Previous owner said the jets were all stock.

wiredgeorge- were the jets sizes you gave me stock, or were they the adjusted sizes needed for high-altitude riding? Or for that matter, do I even need to run different size jets to compensate for the thin air up here in the mountains? From what you say, it sounds like having stock jets might not be the reason my bike is running too rich..

Will it be easy to decipher the jet sizes if I remove them? Are they stamped with a number? And where do I buy different sizes? Are they model specific to the Mikuni, or generic?

Also, do I have to remove the carbs to do this, or can I just drop the float bowl from beneath and access the jets that way? If I do remove the carbs as a whole rack are there any seals I need to be aware of that would need replacement after removing them?

Where do I find wg's tech stuff index and information on coil repowering? I did a site search and found nothing..

Thanks in advance! I appreciate everyone's expertise and generosity.

Post edited by: onanysunday, at: 2007/10/02 12:48

Our website address is in my signature - when you get to the homepage, look in the list of pages on the left.

The jet sizes I noted are what you should use at 7K altitude at moderate temperatures.

If you don't have a Factory Service Manual or Clymers, pick one up. It describes how to remove the carburetors and perform other tune up and maintenance service tasks. The carburetors will need to be removed to check jets or you can do it with the carburetors on the bike. The issue is complicated by the fact that your assembly is an accelerator pump type and all four bowls are linked by gas lines making the removal of one bowl far more difficult. I suggest you just take the carburetors off. The pilot jets usually have the size stamped on the side and the main jets on the top. The numbers may be obscured by crud and you may need to clean the jet with steel wool or a fine wire brush to see the numbers.

The bike should probably be rejetted for altitude but I would wait until other issues have been checked and problems resolved before tackling rejetting. Here are some of the things:

1. check/adjust valve clearances
2. check/adjust cam chain tensioning
3. check resistance of coils and ballast resistor. If these are originals, the resistance may be too high and will yeild poor spark
4. check voltage to coils
5. replace plugs/plug wires and caps

At this point, fine tuning of the carburetors would complete the baseline tuning. I would set the float levels, adjust the idle mixture and then synchronize before rejetting. If you have the stock airbox, change the air filter as well. Reasonably priced K&N drop in filters are available in eBay "STORES"... The airbox on the shafty is unique so these filters tend not to sell well and you can pick one up cheap. Use genuine K&N filter oil to mist the filter prior to use... don't soak it with oil or spray too much on.