Two questions

charwood89 wrote:

My jets are stock. 125 secondary and 62 primary mains. The pods are those cheap Emgo pods, so I'm pretty sure I'm sure I am running a little bit lean.

I figure going up one set one size in jets is wise,
Thanks so much guys,
Casey

Definitely up the secondary main. Go try 135. If you have a 4->1 exhaust the try 140 and 70 for the primary main. I dont think changing the primary main is not as critical. You can get these from Z1enterprises.com

The tiniest bit of gunk in the carbs will plug the pilot jet

Like hoghaterkaw says take a real good look into the Emgo pods. Some of those cheaper ones may cover or block some of the inlets in your carbs

charwood89 wrote:

Thanks very much bountyhunter, that's great help. I'll change out the #1 and #4 shims and maybe the thing will be happier. I don't suppose you have any input on whether I should bump up both the primary and secondary main jet sizes, do you?

Sorry, I only have experience fiddling with the carbs on the 750 twins.

Yup, my pods look just like that. Has that been shown to screw up the performance on the bikes?

Ok, so to resurrect this topic...

I replaced the shims in my No. 1 and 4 valve lifters. Cleaned/Rebuilt the carbs with 135 secondary mains, and I modified my pods by clipping out the restrictive portion of the rubber boot and grinding out the metal lip from the area blocking those orifices on the carbs.

Very quick question. There should be some blowback through the carbs when cranking the bike over dry, correct?


Thanks,

Casey

charwood89 wrote:

...replaced the shims in my No. 1 and 4 valve lifters...Very quick question. There should be some blowback through the carbs when cranking the bike over dry, correct?....

There should be some blowback through the carbs when cranking the bike over dry, correct?

Is this happening on all the carbs?

Blowback through carb may result from a supposedly closed intake valve failing to completely seal.

As known, even with correct clearance, a "burnt" valve may "leak," which disallows complete sealing, especially during combustion.

A leaking intake valve may allow some of the combustion to escape and blow back through the carb.

If not already done, would suggest a compression test.

Adding a teaspoon of oil through the sparkplug hole, and repeating the compression test, might indicate a leaking valve if the compression figure remains about the same. The added oil helps rule out compression being lost past the piston and rings.

A leakdown test could help confirm any suspicions of a leaking valve.

Good Luck!

Yes, it happens on all carbs. I read in another post on this site that if you place your hand over the carb mouth while cranking the bike over, your hand should get covered in gasoline.

I did a compression text when I got the bike about 6,000 miles ago with an even 160 psi across all four cylinders.

Am thinking some valve face damage and/or valve seat damage may have occurred incident to overheating issues during the recent 1600 mile road trip.

Good Luck!

So there should not be a puff of air back through the carbs when turning the engine over with the starter or by hand? That would make more sense to me.

However, I would expect that valve seating issues would have caused more backflashing through the carbs when the bike was running, wouldn't it? Could I possibly be off a link on the cam chain, despite my best efforts to get it right?

I'll run a compression test this morning and see what comes up. Maybe that'll help me figure out a few answers.


Sorry for all the questions, and thanks for the patience.

Casey

charwood89 wrote:

...did a compression text when I got the bike about 6,000 miles ago with an even 160 psi across all four cylinders...

...just finished a 1600 mile trip on my '82 KZ750 E3. The bike ran spectacularly for the better part of the trip...

Could I possibly be off a link on the cam chain, despite my best efforts to get it right?....

Where running fine until the recent overheating episode, I would doubt the cam chain is off a link.

Good Luck!

The compression is down to 100-120 in all four. Forgive my second guessing you, Patton. I'm just not keen on turning this into a major overhaul.

I'll do some more investigating into the valves. The ONLY thing that's still nagging me about this is that the bike rode perfectly until I adjusted valve clearances. It just didn't like to idle or start when hot.

I had decided to blame the idle on some gummy carbs and the hard starting on the tight valve clearances, so this is a bit of a letdown. If the valves really are screwed up, then this is a whole new can of worms.

Ugh. :dry:

Oops, dumb error on the compression test. I forgot to open up the throttle while cranking. I'm getting about 120 psi evenly across all four.

Here's the really weird thing. I dropped a teaspoon of oil in like suggested, and the compression did jump. All the way to 180-200 psi. I'm not sure of what to make of that.

:blink:

I believe the addition of oil to the cylinders is intended to show whether compression leak-down is caused by improper sealing of the rings against the cylinder walls. The idea being the oil will help seal that are but will not seal the valves of head gasket. Based on that theory, it sounds like your valves are sealing pretty well.

One question does occur to me regarding the jump in compression in any engine when oil is added to the cylinder: all else being equal, what is the affect of the oil on cylinder head volume? In other words, by adding oil (which is virtually incompressible) to the cylinder the remaining volume of the cylinder head is reduced when the piston is at TDC. The oil has a similar effect of a high dome piston in increasing the compression ratio by taking up space in the cylinder head. Picture the affect if 10 tablespoons were added; compression might jump to 50:1. The question I have is this: what percentage of cylinder head volume does 1 tablespoon of oil represent, and what is the resulting compression ratio? The reason I ask is that any increase in compression ratio will raise the PSI indicated in a compression test, so how can one determine how much of that PSI increase is related to the improved ring/cylinder wall sealing and how much is related to the increased compression ratio? Inquiring mind want to know. Ed