TOPIC:

Hi
Need some tips. Did a total rebuild on my ZN1300 last winter. New cam chain, primary chain, Liska idler gear, pistons rings ++ The cylinder head was delivered to the machine shop. They did a nice job. However, they said it was necessary to replace the intake cam and got me another one (hopefully it was from a ZN1300). I put the engine together and it fires right up. But I discover a sluggish throttle response. Didn't investigate it closer. I warmed up the engine, bleed the air, retorque the head and put it to winter storage. All good.

When I start the engine now, throttle response is still sluggish. I have new vacuum sensor and vacuum hoses. As shown in pictures there is magnificent low vacuum in manifold 3 and 4. And I wonder what could be the reason? Any ideas?

Thanks

The first thing I would check would be the valve clearances. You did a complete valve job recently and as the valves seat in to the valve seats, the clearances usually tighten up. So start there.

I would also change a couple of your test gauge hoses around and see if maybe your gauges are not reading properly.

The common link between the 3-4 cylinder is the rubber boot between the middle carburetor and the head. Check for a vacuum leak at the boot to the intake flange and boot to the carburetor.

I should also add that I see you are only measuring 3 of the 6 intakes and while that's fine for balancing carbs, it doesn't tell the whole story when trying to diagnose a problem. The intakes are split all the way through including the carbs. So you may also want to check the other 3 cylinders by moving your test gauges around.

I checked the valve clearances. Numbers in parentheses are the requirements for the Voyager.
Cylinder 1 2 3 4 5 6
Exhaust gap (0,15-0,25 mm) 0,28 0,22 0,20 0,16 0,26 0,27
Intake gap (0,05-0,15 mm) 0,12 0,14 0,11 0,11 0,15 0,12

Exhaust gap in cylinder 1, 5 an 6 is a bit loose. But it is enough to create trouble?

When I did the vacuum test I moved the gauges around, no difference.

I don't know that I would be racing out to get new shims but if you have the next size up, I would reshim back into specs. I would like to think that over time, the clearances will tighten up.

your reporting of 18 in. of mercury is very interesting. That's typical of most engines at idle but here at KZ1300.com most members who have checked and set up their carbs report intake vacuum down in the 10-12 inches of mercury as being normal and I've always questioned that as unusual. With 270 duration cams, I might believe 13-15 inches of mercury as normal. As of this point in time, I've not had a KZ1300 running in my presence so my knowledge base is strictly based on my experience working with "other" engines as a automotive mechanic.
Since you've measured the clearances and not found a tight valve, something else is just not right. Either you have an intake leak or the butterflies in the 3-4 carb are more open than the other 2 carbs.

Kawboy !!!! Surprised you missed this one !! Suffering from too much "T" ?


His gauges are calibrated cm/Hg