Author Topic: Frustrated..can anyone help (Read 1252 times)

BackRoads · « **on:** May 08, 2013, 10:28:50 pm »

First i would like to say hello to everyone. You have a great site here.

I'm having an issue with my engine and cant figure it out. When you let off the gas it will rev down most of the way...but it takes about 10 or so seconds after that to go all the way to idle. From past experiences that would tell me I have an air leak but after the engine was completely rebuilt, the builder did a leak test and said it was good. I am also confused with the jetting on it. I have a pwk 38 air striker and according to the jetting i have heard of most people running, I would think its running lean(52 and 165) but I did a plug chop and it looks good. If I richen the jets up, it doesn't want to run right...loads up real bad and doesn"t seem to clean out at all...Am i overlooking something? Do the air strikers work on these?
Heres my setup...

.100 over Wiseco piston
PT pipe
38mm air striker carb
Vforce 3's
porting but not too crazy
squish was done
cool head...not sure of dome size
uni filter in air box with lid
all new bearings and seals inside the engine
running 110 octane race fuel
jets 52,165 and I believe a deg needle. not sure of the slide

1986QuadRacer · « **Reply #1 on:** May 08, 2013, 10:48:04 pm »

carbies is tight, boot is not old or ****? I'd spray a little wd/40 around the intake or jb and see is the revs change. don't use carbies cleaner it might rev up faster than ya want. or ether. pipe is nice and tight?

BackRoads · « **Reply #2 on:** May 08, 2013, 10:55:46 pm »

I tried that and the rpm's stayed the same. Boot is in great shape. The pipe is tight up front but i do notice smoke coming out where the silencer meets the pipe in the middle of it (at start up). No smoke at all up front

1986QuadRacer · « **Reply #3 on:** May 08, 2013, 11:07:26 pm »

ya that won't matter there. but try to seal it up with a pop can and a couple clamps or something. have you checked the plug idling or at a high idle when it warm to see what it looks like? was the plug chop you did at high speed? did you try a fatter pilot jet? and did the weather change since you did it?

BackRoads · « **Reply #4 on:** May 08, 2013, 11:11:22 pm »

i did a high speed chop, idle chop and a chop after normal riding. all looked good. I went one size richer on the pilot and the bottom end was real sluggish and wouldnt run right. i did the testing in 74 degree weather at 1050ft elevation.

BackRoads · « **Reply #5 on:** May 08, 2013, 11:16:09 pm »

it seems like drastic changes in how it runs with going up or down a size in jetting. if i go to a 50, its hard to start and kicks back...if i go to a 54 it doesnt want to run good at all. Im lost... I dont want to give up on it because its been my dream quad since i was a kid but its getting to me haha

BackRoads · « **Reply #6 on:** May 08, 2013, 11:17:57 pm »

also...the air screw is out 2 turns

1986QuadRacer · « **Reply #7 on:** May 08, 2013, 11:46:03 pm »

a little kickback? ya. it's probably the seal on the clutch side. no biggie. I put two in last year;) the first one didn't have grease on it or loctite. you might want to dump the oil and look for rubber pieces or do a leak down. mine was smoking more than usual but you can barely tell.

Maxxh2o · « **Reply #8 on:** May 09, 2013, 12:40:06 am »

pwk's are hard to dial in on big bores. what elevation are you at. if anywhere near sea level you should be around a 180 main. Check both float vent hoses / circuits and the float levels. I've melted one of the vent hoses on a pipe and it ran like poo till I figured it out.

Dwilkins126 · « **Reply #9 on:** May 09, 2013, 03:12:36 am »

I have the same issue with mine on a stock TM34SS carb (220 main, 30 pilot, 2nd clip on needle 1.5 turns on air screw) but it only lasts a few seconds. I have it bored to 68mm, uni filter with lid on the airbox, boysen power reeds, FMF Fatty, running 32:1. I am at 55' elevation and the temp today was ~80 degrees. During my break in riding I had the stock 240 main and 3rd clip on the needle at about 70-75 degrees and didn't have the issue but it ran rich. I think I am going to get a leaner needle and try one size smaller on the pilot.

If you or someone else figures it out let us know. I will take any advice to help me figure out the jet settings.

PS: I see you guys talk about squish...can someone enlighten me on what this is please...thanks..

Rider414 · « **Reply #10 on:** May 09, 2013, 04:00:16 am »

Get rid of that PWK! So many people have a hard time tuning that carb.

BackRoads · « **Reply #11 on:** May 09, 2013, 04:17:12 am »

I'll check it out but all bearings and seals are new.

BackRoads · « **Reply #12 on:** May 09, 2013, 04:24:01 am »

Quote from: Maxxh2o on May 09, 2013, 12:40:06 am

pwk's are hard to dial in on big bores. what elevation are you at. if anywhere near sea level you should be around a 180 main. Check both float vent hoses / circuits and the float levels. I've melted one of the vent hoses on a pipe and it ran like poo till I figured it out.

I'm at 1050ft elevation. I'll check everything you mentioned

BackRoads · « **Reply #13 on:** May 09, 2013, 04:29:42 am »

Quote from: Rider414 on May 09, 2013, 04:00:16 am

Get rid of that PWK! So many people have a hard time tuning that carb.

I was really thinking about trying a different carb. Should i go with Mikuni? What size for my set up?

MotorGeek - Jerry Hall · « **Reply #14 on:** May 09, 2013, 07:06:12 am »

Quote from: BackRoads on May 09, 2013, 04:17:12 am

I'll check it out but all bearings and seals are new.

You are experiencing the result of a poorly designed carburetor. This is why I do not recommend ANY of the Keihin carbs on the LTs.

No matter what needles, air screw setting or pilot jet combination you try, it will be sloppy rich down low or have the ring ding dings.

Kyle T · « **Reply #15 on:** May 09, 2013, 08:35:34 am »

Ah HA! So that's why mine never ran well with a Keihin...

BadMoonRacing500 · « **Reply #16 on:** May 09, 2013, 09:55:43 am »

Is this a 250 or 500? If it's a 250 the stock mikuni tm34 bored out works good or a stock tm38 from a zilla. If it's a zilla get a Stock tm38 and send it to Jerry Hall to be bored out to 41.5. Keihin and lectrons are notoriously hard to tune. I run Mikuni's on everything but my, 87 250x.

Q2W · « **Reply #17 on:** May 09, 2013, 01:32:54 pm »

Get in line. Most people have felt the woes of the keihin here.

Dezsled · « **Reply #18 on:** May 09, 2013, 04:39:35 pm »

I got a 39 pwk on my 500, no airbox lid 180 main 58 pilot 6.0 slide dgh needle 4th clip down

These carbs work great on trx250rs

BackRoads · « **Reply #19 on:** May 09, 2013, 05:03:54 pm »

Thank you guys for all of the help. Anyone here selling a Mikuni thats already bored?

Dezsled · « **Reply #20 on:** May 09, 2013, 05:24:13 pm »

I was on the look out for one also... But I think I'll be going on flea bay for a new one then send it out to HPR.

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Author Topic: Frustrated..can anyone help (Read 1252 times)

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