Auto Technologies Head swap frustration

Thanks for all your replies.
Have been using the prescribed iridium plugs, tried the champion N7Y also today. Have not yet looked at plugs stopping from speed. Generally though, the electrode part is okay, slightly sooty surround. Have played with different jet sizes and needle heights etc, etc. previously had 106 needle jet, no difference. Spray tube is the 622/074. Needle has 3 grooves. This is standard spec, or one of em!! A carb supplier felt I should have a cutaway spray tube fitted??. will check present tubes are seated correctly.

It does seem to be RPM related and not throttle position.

Ignition is a recently replaced Tri-Spark unit. Coils are also from Tri-Spark for that extra oomph! Neither of which has done more than 30 miles as things are. Surely it cant be the unit again. Have binned the Boyer so cannot appease my be it ever so faint nagging curiosity. :|

Am back to using the original longer pushrods again. I dont feel this can be the problem can it, as the tappet adjusters allow me to set 8 thou inlet and 10 thou exhaust?

Have recently adjusted the cam chain also. That said it is audible when revving on tickover.



Aries

I'd be putting my old ignition back on about now and giving it a try. The cam chain noise is a bit weird as well. Since you know the head is a bolt on item and are fairly certain it is good and since you've checked about everything else and it seems in order. Did you go back and double check the things you personally changed to make sure they are ok.

britbike220 said:

Put your old ignition back on and give it a try.

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Curiosity dictates I would if I still had it, but it departed my garage in a clear out. Yes, I am kicking myself.!!!

Can you borrow one. If you were a bit closer :lol: I'd loan you the new pazon I have sitting on the shelf.

aries said:

Thanks for all your replies.
Have been using the prescribed iridium plugs, tried the champion N7Y also today. Have not yet looked at plugs stopping from speed. Generally though, the electrode part is okay, slightly sooty surround. Have played with different jet sizes and needle heights etc, etc. previously had 106 needle jet, no difference. Spray tube is the 622/074. Needle has 3 grooves. This is standard spec, or one of em!! A carb supplier felt I should have a cutaway spray tube fitted??. will check present tubes are seated correctly.

It does seem to be RPM related and not throttle position.

Ignition is a recently replaced Tri-Spark unit. Coils are also from Tri-Spark for that extra oomph! Neither of which has done more than 30 miles as things are. Surely it cant be the unit again. Have binned the Boyer so cannot appease my be it ever so faint nagging curiosity. :|

Am back to using the original longer pushrods again. I dont feel this can be the problem can it, as the tappet adjusters allow me to set 8 thou inlet and 10 thou exhaust?

Have recently adjusted the cam chain also. That said it is audible when revving on tickover.



Aries

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It sounds like you have covered most of the jetting possibilities without any real change in the problem. I would take a look at the spray tubes for sure. And then I would give the ignition a close look. Make sure the connectors are all crimped correctly and you don't have a broken wire somewhere. Make sure you have an engine ground. Check your plug wires. High resistance from an incorrectly installed wire end or a bad resistance wire can cause symptoms like yours. Electrical interference from poor alternator connections or loose ignition switch terminals can raise havoc with the digital timing system in a tri-spark. If you have your old coils you might want to give them a try also. You wouldn't be the first one to receive a weak new coil. Jim

I noticed Hobot mentioned this, but never saw a reply on it. Are you certain the needles have not come loose off the clips? I went thru a similar problem last spring when one of my needles kept coming out of its clip. About drove myself crazy until I bought new clips.

Russ

aries said:

Spray tube is the 622/074. Needle has 3 grooves. This is standard spec, or one of em!! A carb supplier felt I should have a cutaway spray tube fitted??. will check present tubes are seated correctly.


Aries

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The groove that we speak of are not the clip grooves but the itty bitty grooves above them. These are the Id grooves. If you have 3 id groove than this is a 2 stroke needle. I think your supplier is incorrect. Cut away spray tubes are also for 2 stroke but were also used for late 850's. This mid range faulting is indicative of needle and needle jet issues, possibly even throttle slide.
2nd one in is what you should have, 4th one is what you may have, and 3rd one is what you say you have.


Go here for more. Scroll down for needle and spray tube info.
http://www.amalcarb.co.uk/TechnicalDetail.aspx?id=11

pvisseriii said:

rvich said:

OK guys as usual it has been worth it to sort through this thread as I am learning stuff I never knew I would want to know. It is rather off topic, but there is a comment early on that some suggest that not polishing intake manifolds is preferred as the rough surface and turbulence improves flow? I don't get out much, but this is contrary to everything I thought I knew.

Russ

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Read this http://www.mototuneusa.com/homework.htm about half way down the page "Why Not Polish The Ports ??"

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BTW-thanks on that. I still think it is a good idea to remove casting flaws that hang in the intakes like stalagtites, on mine I reached in there with some 100 grit and removed them. Lucky for me I am too lazy to polish them!

Thanks guys for all your help and ideas. Will check things over again and keep fingers crossed I find the gremlin/s.
Will update on the forum when that moment arrives, so no one hold their breath!!!

Aries

Russ[/quote]
Read this http://www.mototuneusa.com/homework.htm about half way down the page "Why Not Polish The Ports ??"[/quote]

BTW-thanks on that. I still think it is a good idea to remove casting flaws that hang in the intakes like stalagtites, on mine I reached in there with some 100 grit and removed them. Lucky for me I am too lazy to polish them![/quote]


Removing casting laws is good. Mondello said that 50 to 80 grit was the best finish for intake ports. He said too fine a finish encourages fuel to condense on the port wall and travel into the cylinder as a liquid. I know that when tuning the fuel injection I have to increase the transient acceleration enrichment if the port is polished. It also shows as a less stable CO reading on exhaust gas.
Polishing the exhaust port may help to cut down on carbon buildup .
Port finish makes no change at all to flowbench readings. Jim

Texturing by pits, lips and notches and grooves is a known flow streamlining and turbulence mixing method that is done AFTER the basic path is cleaned up from casting errors and bad mis matching of ports mating. Too much junk in way of mixture flow does what we all expect, slow and disrupt the flow. Tricky trial and error to get port texturing to help and not hinder power, especially at hi flow rates. I purely lucked out in a couple of my cases, only the out board was done in attempt to see what happened. Ms Peel wonder was pure down and dirt way to get it running to break in rings before CHO big port narrow valve stem head returned home.

A two valve head has potential to beat a 4 valve head at slower flow rpm rates because as piston hits TDC the mixture gets so thick it stops mixing much, 2 valves make mix swirl more than 4 valve mix tumble, so stays in more motion to spread flame kernal flame fronts. Staggered opening and intake valve size in 4 valves can add swirl so can beat a 2 valve, across the scope in torque and hi rpm flow.

Part of proving ones man hood or luck of grace from above is persistence to keep diddling all the combos possible till joy and understanding arrives.

A small well tuned engine is nicer to run than a big boy that is mis firing or failing to rise in power as expected.

I had a V8 build up by race shop, optimized for propane, not gasoline by using my meager understanding and I won a bet with the dyno guy by making more power than the LPG evaporator was rated to flow in hp feeding. It only matched the evaporator rating, until I spent $200 more to test advancing cam one more 0.5 degree. Worked a treat on gas too and most amazing was that LPG has 15% less power than gasoline, but my engine was only 6% below the dyno curves of hp/trq on gasoline to break in rings/cam initially. Only dropped in power as rpm rose above evaporator fuel flow d/t finger size needles needing some sanding down, which I never got around to before I moved Ozarks. Cam shaft chosen was a jet boat torque cam, not road going hot rod cam, but under 13 sec 1/4 ET in 4800 lb 3/4 ton van allowed me to tease the Porsches on Houston freeways : ) It had handling mods that made it a delight to drift and dance rear like the stunt cars do. Trouble hit at 120+ d/t lift and wind gusts on barn wall sides. Oh it'd go faster but I couldn't take it : (

I am anxious to see the outcome of this issue. I believe it will be fairly untechnical.

Has there been an update or resolution to this mystery?

aries said:

Hi Folks.
I had fitted carbs and ignition before changing to the new head. Bike was running very well. Was hoping it would be a straight forward head swap!! Have also timed the bike using a disc to the camshaft.
Obviously compression has been reduced with a higher head rather than the skimmed combat head, which keeps bringing me back to carburation, but have tried most things except for a different spray tube. Presently have one without the cut-away

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do not change to a cut-away as these were designed for 2-strokes and mk3 with those plastic boxes
What are you running as airfilters at the moment?

Seems an awful lot of trouble to go about diagnosing a problem which may well be easily sorted out with an hour on a rolling road dyno?

aries said:

Thanks guys for all your help and ideas. Will check things over again and keep fingers crossed I find the gremlin/s.
Will update on the forum when that moment arrives, so no one hold their breath!!!

Aries

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Aries,

What was the final outcome here? If you were able to resolve the issue(s), please provide the courtesy of a summary for all interested parties and those that offered help and advice.

aries said:

Thanks guys for all your help and ideas. Will check things over again and keep fingers crossed I find the gremlin/s.
Will update on the forum when that moment arrives, so no one hold their breath!!!

Aries

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Well it's a good thing you let everyone know not to hold their breath.



Does anyone else know if the problem was solved, and what was causing the problem?