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Author Topic: Sea level riders - What’s richer than a dgh ?  (Read 3691 times)

Offline atvmxr

Sea level riders - What’s richer than a dgh ?
« on: April 10, 2021, 09:34:07 PM »
My bike came from Kansas.  Was lean everywhere at sea level down here in Houston tx.  It had a cel, I switched to a dgh, but it’s only borderline right with the clip on the very bottom. I upped the pilot and main 2 sizes also.   What’s the next needle to get so it’s in the middle position?

Stock jug, 80 over, ported for mx, cool head with 21 dome, 38 as, esr trx5b pipe, c12 or sunoco 110 fuel with 927 at 40:1
55 pilot, 175 main

It runs great, but I can still hear slight detonation and the plug is very light tan with grey specs.
Bunch of race quads that run on premix

Offline The norm

Re: Sea level riders - What’s richer than a dgh ?
« Reply #1 on: April 10, 2021, 11:46:45 PM »
An E series needle is the next richest on the needle chart. I run DGH needles on all my R's at sea level and seem to have good luck with them. I wonder if you have a small air leak?
Loren
1986 Trx250r-- Hybrid Engineering 391(Good bye super 310)
1986 Trx250r-- Hybrid Engineering  ported stock 86 cylinder
1986 Trx250r-- craigslist engine with unknown ported 89 cylinder.
1985 Atc250r-- Needs a lot of work (Super 310's new home)

Offline 2ndmoto

Re: Sea level riders - What’s richer than a dgh ?
« Reply #2 on: April 11, 2021, 02:29:41 AM »
You riding at 3 palms?

Offline havinnoj

Re: Sea level riders - What’s richer than a dgh ?
« Reply #3 on: April 11, 2021, 02:03:31 PM »
My bike came from Kansas.  Was lean everywhere at sea level down here in Houston tx.  It had a cel, I switched to a dgh, but it’s only borderline right with the clip on the very bottom. I upped the pilot and main 2 sizes also.   What’s the next needle to get so it’s in the middle position?

Stock jug, 80 over, ported for mx, cool head with 21 dome, 38 as, esr trx5b pipe, c12 or sunoco 110 fuel with 927 at 40:1
55 pilot, 175 main

It runs great, but I can still hear slight detonation and the plug is very light tan with grey specs.


To confirm, when you say borderline - you want the bike to be even richer?   What part of the throttle position(s) are you wanting to change?

Needle markings: Taper ----------------------> Length ---------------> Diameter
Which translates: 1/2-Full throttle -----> 1/4-Half throttle-----> 1/8-1/4 throttle

By moving from a CEL to DGH, you richened the needle all around.   

There is overlap in needle clip positions -- for example a CEL in #1 position will be the same as CGL in #3 position. 

In the D series (and most series), the xGx is the leanest length you can get.  So you could step to a DCH which will richen the length considerably.  Even moving to the Exx series - you could run the EEH for example which will richen both the Taper and the Length.  Or if you need even richer Length, you could go to the ECH.  Just depends on which throttle positions you're trying to richen (I am assuming that richen is what you want to do). 
« Last Edit: April 11, 2021, 02:47:25 PM by havinnoj »

Offline 2ndmoto

Re: Sea level riders - What’s richer than a dgh ?
« Reply #4 on: April 11, 2021, 11:14:10 PM »
Sudco used to have nice diagrams in their catalogs. Not sure if they still do.

Offline atvmxr

Re: Sea level riders - What’s richer than a dgh ?
« Reply #5 on: April 13, 2021, 03:10:56 PM »
it sounds like I need a DEH per what OJ said.  That in the #3 clip should be the same as the DGH in the #5?
the 1/2 to ~3/4 throttle was the trouble spot im trying to get richer with the needle change. 

slight air leak is possible, maybe from crank seals?  quad has always had a quick rpm increase on start up for ~5-10 seconds before it idles down.  messing with pilot and air screw seem to make no difference. 

yes I was at 3 palms, had a cool front come in so it was like 60-65 degrees when I was out on my practice laps.  During the first moto it was 80 or so and the clip in the #5 spot seemed to work.
Bunch of race quads that run on premix

Offline Jerry Hall

Re: Sea level riders - What’s richer than a dgh ?
« Reply #6 on: April 18, 2021, 10:57:37 AM »
it sounds like I need a DEH per what OJ said.  That in the #3 clip should be the same as the DGH in the #5?
the 1/2 to ~3/4 throttle was the trouble spot im trying to get richer with the needle change. 

slight air leak is possible, maybe from crank seals?  quad has always had a quick rpm increase on start up for ~5-10 seconds before it idles down.  messing with pilot and air screw seem to make no difference. 

yes I was at 3 palms, had a cool front come in so it was like 60-65 degrees when I was out on my practice laps.  During the first moto it was 80 or so and the clip in the #5 spot seemed to work.

All engines are lean on start up.  Engine heat has an enriching effect on the mixture.  The piston crown heats up rapidly and the rest of the engine takes more time.  If you had crank seals leaking, why would they only leak the first 5 to 10 seconds?

Offline atvmxr

Re: Sea level riders - What’s richer than a dgh ?
« Reply #7 on: April 19, 2021, 11:26:15 AM »

All engines are lean on start up.  Engine heat has an enriching effect on the mixture.  The piston crown heats up rapidly and the rest of the engine takes more time.  If you had crank seals leaking, why would they only leak the first 5 to 10 seconds?

well that was more to norms point that he thought I had an air leak at all rpm ranges since the DGH is working fine for him.  I dont know the details of how crank seals start leaking.  If it was between the inner part of the seal and the crank snub, maybe its a gap when the motor sits, as rpm builds on first start up the leak lessens, and then later on when Im on it hard coming out of corner on the MX track the vacuum pulse of the motor causes it to start leaking a little air again?  LOL  just spitballing. 
Bunch of race quads that run on premix

Offline Jerry Hall

Re: Sea level riders - What’s richer than a dgh ?
« Reply #8 on: April 19, 2021, 09:28:30 PM »
Norm may be right that you have an air leak and the DGH may be right for him.  You could have identical engine packages ( pipe, porting, carb, ignition, reeds, intake,etc.. ) but your Keihin carb may need a different needle to perform like Norms carb if you installed your carb on Norm's engine.  I find that the needles and needle jets wear out on these carbs and often require the constant diameter portion of the needle to needs to be increased as the mileage on the carb increases.   

The lips of the crank seal may have a few thou clearance or very little grip on the crankshaft when it is at the end of is lifespan and cold.  Sometimes it takes a few hundred engine revolutions for the seal to gain a enough heat and lubrication to begin sealing on a cold start.  A vacuum test on the crank case will usually find this problem while a pressure check may not find the air leak in this situation.  Do this vacuum test on a cold engine.

« Last Edit: April 19, 2021, 09:30:39 PM by Jerry Hall »

 

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