Rear Cylinder firing off??? and RPM's slow to fall

[jcbell1007]

So I'll put this out to the NESR crowd as well.

Working on my hawk with Doc tonight and ran into a couple of problems. Found that the rear cylinder doesn't seem to be running at hot as the front. It is noticeably different when you touch the front and rear headers. We checked and the rear cylinder is getting spark to both plugs. I also re-jetted the carbs tonight to 150 mains on the front and rear down from 162/160.

Also noticed that the RPM's don't fall as fast as they should. RPM's seem to build normally, but the RPM's gradually decline over a second or two down from 6k or so Vs almost immediately.

Hawk has pod filters and a 153x1 cam which is a little hotter than stock.

Doc is thinking its a carb or timing issue... any other thoughts?

[butcher bergs]

Carb. The slow engine decel suggests a lean condition, IMO.

How far did you take the carbs apart? If it's equipped with one, perhaps the emulsion tube is reversed in the carb in the affected cylinder.

If you went down on the jets it's possible that your air mix screws need to be turned in accordingly.

The idle adjustment can also be a cause of slow engine decel. You might be experiencing the results of more than one issue....something to keep in mind.

[Doc]

Went down with the jets and turned the mix screws up a lil which helped to keep my eyes watering from the fuel fumes prior to (was running VERY rich)

I am not as concerned with the slow drop in idle as I am the rear cylinder issue. We had swapped the heads on this motor and I am hoping we got it right.

[jcbell1007]

I went leaner because it smelled really rich out the exhaust and tons of backfiring. Slow revs (only when falling at closed throttle) happened when the larger jets were in it as well.

I left the stock emulsion tube in instead of putting in the ones that came with the stage 3 factory kit.

I readjusted the mixture screws according to the literature that came with the kit, 3 turns out.

idle adjuster screw seems to be higher than normal according to doc. He did mention that with idle adjuster screwed in a lot will cause a slow drop in rpms, but it needs to be adjusted open so that it idles at about 1k.

maybe i need to change the emulsion tube, not sure what to do with the idle then, bigger idle jet? 145 instead of the stock 142?

[butcher bergs]

Blockage in one of the carb passages?

I'd say pull the carbs, drain all fuel from them and blast any and all passages with compressed air.....least that's what I'd do.

How far away are you from stock jetting? Sizes?

[jcbell1007]

Stock is 135/132 respectively with a 42 pilot/idle jet.

I'm at a 150/150 main with a 42 pilot. carbs were just cleaned a short time ago after old VP race fuel sat in them for 1 year plus.

[Doc]

Jetting is close for a Hawk with pods and exhaust. Even if it is a stock motor.

We all run stock pilots and no one changes the tubes.

There might be a small clog somewhere but again I am leaning toward air issues or timing.

[BLACK SQUIRREL]

Let me guess you got it from DOC

[Doc]

Let me guess you got it from DOC

:

[Kurlon]

This screams clogged carb to me too... one cylinder running cold, idle having to be jacked (so the working cylinder is well off the pilot circuit) and way rich... If it was a timing issue I'd expect back firing/knocking.

[BLACK SQUIRREL]

doc is helping you fix it?


Thats like stealing someones wallet then helping them look for it.









JK/ Doc is a good man but an easy target

[butcher bergs]

If it were timing you'd know for sure via slammed valves, random almost-nuclear back firing, engine seems to want to jump out of the frame, won't run at all, won't idle at all, starter struggles when turning the engine over.

Based on descriptions here, nothing suggests timing but I've been wrong once before.

[SVRACER01]

Working on my hawk with Doc tonight ...

well theres your problem right there

[Doc]

Timing just off a lil or the valves clearance off?

[butcher bergs]

It's either timed or it's not. If not, you'll know.

A cool pipe suggests no fuel supply and "no" on the valve clearances.

[Doc]

Guess I was looking too deep.

I figured the carbs were clean and put together right. I will double check them.

A cool pipe suggests no fuel supply.

Or no spark.

[FTMS]

Start simple, check compression since you said you replaced the head. What do the plugs look like? I don't know the carb set up on those but if it like my VTR's the carb boots can be a pain in the ass to get the carbs to seat fully. Check for a vacuum leak around the boots. Have the carbs been sync?

[TLRMan]

Air leak, or idle circuit not providing fuel.
The rear cyclinder isn't running at Low RPMs.
Comp test will show if the top is buttoned up right, but Me thinks it's carb, or air leak related. Carb sync being off will also cause engine to hang before idling.

[CEO]

Air leak, or idle circuit not providing fuel.
The rear cyclinder isn't running at Low RPMs.
Comp test will show if the top is buttoned up right, but Me thinks it's carb, or air leak related. Carb sync being off will also cause engine to hang before idling.

Mine was hanging up above idle too before we dropped the needle a click and adjusted the a/f screw, remember? I only have one carb though...

[The Crashing Tomato]

bwahahahaha ..... JCB when I first met DOC he "WARNED" me about Hawks and that I'd be better off with something more reliable like an SV or a Ducati ...

I now have several Hawks that run trouble free and still hear (now from you) that it's just DOC's Hawks that are the trouble.

DOC

JCB just take the carbs and UN - DOC them.

p.s. TLR man has the goods follow his lead!!!!!

Mark and GF

p.s.s. JCB I have a cache of parts for that baby at a good price ..... PM me when you are in need

[jcbell1007]

Ok. Lots of good info here, I'll have to tear into it tonight/tomorrow and hopefully get it track worth in the next couple of days.

The one thing I didn't check on is the float valves. both looked to be at the same height but I didn't check or adjust. I'm gonna take it all out and clean everything/replace everything again and we'll see what happens. Compression I'm not sure if I will be able to check. How would I check for an air leak?

Pulled one of the rear plugs last night and it was grayish which I read to be normal firing. It was a little oil covered at the moment because of trying to start it and being partially flooded. it wasn't black (rich) or on the white side (lean).

[butcher bergs]

How would I check for an air leak?

Run the motor and spray a flammable mist anywhere post-air filter (carb boots, etc). I use light sprays of ether (Starting fluid) or WD40 and listen for a change in idle speed......I stress using LIGHT sprays of ether.

[KB]

I'm going with timing off.

KB

[Doc]

bwahahahaha ..... JCB when I first met DOC he "WARNED" me about Hawks and that I'd be better off with something more reliable like an SV or a Ducati ...

I now have several Hawks that run trouble free and still hear (now from you) that it's just DOC's Hawks that are the trouble.

DOC

JCB just take the carbs and UN - DOC them.

p.s. TLR man has the goods follow his lead!!!!!

Mark and GF

p.s.s. JCB I have a cache of parts for that baby at a good price ..... PM me when you are in need

I did not clean the carbs. Jason did. My failure. I will clean them tomorrow and all will be right in the world.

[jcbell1007]

I did not clean the carbs. Jason did. My failure. I will clean them tomorrow and all will be right in the world.

First time ever tearing into carbs, cleaning carbs, etc... I've never been exposed to this before and was grateful for the help. I'm not surprised that I may have missed or muffed something up. thank you again for trying to correct this for me.