DOHC jetting problem

wrstar

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Everett, WA
1982 xs400rj seca
airbox delete, now using EMGO 52mm pods
hesitate when high rpm (>5500-6000), will get worst when full throttle (WOT)

according to service manual, stock jets are LHS127.5 and RHS117.5
jetted to LHS132.5 and RHS122.5
got better then pods with stock jets, but the hesitate still exist

havent have the 18mm spark plug socket to remove the plugs to see whats going on
but the plugs are fairly new (NGK D8EA)

Any idea guys? Thanks in advance
 
6000 rpm is mid range on DOHC engine. Wind it up!

An 18mm wrench will also work to remove sparkplugs.

Now that you have pod filters, you should be able to match the main jets.
 
For the pods you will want to move the jet needles up a notch (if yours has notches) or use a spacer to move it up about .5-1mm. Also you will want to put in two identical jets, old ones were offset because of the offset airbox, probably start around a 140-145 with pods.

This is what I had to do to get my 3wheeler with the dohc to run good, I had the same issues with pods, hesitated and hit a wall in the mid range
 
ok guys here comes the pics of the plugs
ran to autozone and got a 18mm spark plugs socket
the plugs in the pics are in correct LHS/RHS order (LHS plug is on the LHS of the pic, RHS plug is on the RHS of the pic)

biggest problem i found out is the gap on the RHS plugs is weird

sooo the LHS plug's color looks about right, brownish
RHS looks a bit white

anyway, since the gap is messed up im gonna get a pair of new plugs tmr
stick to the stock spec, NGK D8EA? or anything else?
 

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well the reason why i used offset jets are i really dont know much about carbs..
and i dont know if i use same size jets will affect my sync..
really dont wanna mess around with carbs..
im a broke a$$ college guy live in an apartment, no garage..

about the notch thing idk anything about it, since the furthest step i will mess around with my carbs is open the bottom cover.. knowledge and tools limitation.
 
*off topic
re 16vgtidave:
ur user name sounds like u r a vw guy too
i drive a 2000 passat 1.8t
early gtis are so awesome

vw and dohcs both are same.. good to meet you
 
That's no problem, the offset airbox created different levels of vacuum at the carburetors and it needed the two different sizes so that it would pull the same amount of fuel at each, even though one would have a higher vacuum than the other. Okay, the notches are under the top cover. There is a slide under there with a needle sticking out of it, because the pods create less vacuum the needles need to be moved up so that the lower vacuum can pull the right amount of fuel. To do this in the center of the slide are two screws, if you remove them there will be a spring under the small plate that holds down the needle, to raise the needle just go to the hardware store and get six small washers that fit down in there, they will cost a few cents. Start with two washers under the clip on each needle. But the main jets will need to be the same, if you are around 2500ft above sea then a 145 jet is the place to start. The synchronization will most likely need to be redone, I can take a few pictures of how to do it for about $5.00 if needed.

I will get some pictures of how to adjust the needles tomorrow morning for you

Small washers:

IMG_20130816_225655.jpg
 
That's no problem, the offset airbox created different levels of vacuum at the carburetors and it needed the two different sizes so that it would pull the same amount of fuel at each, even though one would have a higher vacuum than the other. Okay, the notches are under the top cover. There is a slide under there with a needle sticking out of it, because the pods create less vacuum the needles need to be moved up so that the lower vacuum can pull the right amount of fuel. To do this in the center of the slide are two screws, if you remove them there will be a spring under the small plate that holds down the needle, to raise the needle just go to the hardware store and get six small washers that fit down in there, they will cost a few cents. Start with two washers under the clip on each needle. But the main jets will need to be the same, if you are around 2500ft above sea then a 145 jet is the place to start. The synchronization will most likely need to be redone, I can take a few pictures of how to do it for about $5.00 if needed.

I will get some pictures of how to adjust the needles tomorrow morning for you

thanks, ill let u know if i need them
money is running low, and my car needs fixing so there will be a delay..
 
*off topic
re 16vgtidave:
ur user name sounds like u r a vw guy too
i drive a 2000 passat 1.8t
early gtis are so awesome

vw and dohcs both are same.. good to meet you

You are correct. 1987 GTI. Auto-X prepped and barely street legal. 2.0 16V... And many more changes. My Maxim is more fun... ;)
 
I am running 145 jets with pods I'm about 2400ft mark and my needle is in the third notch out of five any ideas if this is correct settings maybe its why I'm using so much fuel
 
Devdg- What do your sparkplugs look like? Where you are at should be very close, needle may need a slight adjust. Do you have a stock exhaust?

Wrstar- here's a picture of what is in the slide, washers need to be placed on the needle below the clip but above the round plastic guide on the needle

20130817_092238.jpg
 
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I'll pull the plugs and look when I get home. Cannot say for sure if it is stock or not but l have to replace the head pipe and the gaskets due to a pothole and a broken muffler mount

Good to know its close the air screw was 1 turn out I cannot say for sure what my pilot jet is since I cannot read any numbers on it. I have my air screw out to three and once I get it back on the bike ill know if I got it cleaned out and working better
 
sparkplugs were fouled so i cleaned them and now with the cleaned carb it has alot more power just a studder at 6k sounds like a old hit and miss engine and it only does it when its under load. any thoughts?
 
sparkplugs were fouled so i cleaned them and now with the cleaned carb it has alot more power just a studder at 6k sounds like a old hit and miss engine and it only does it when its under load. any thoughts?

what jets are u running?
 
ok guys heres a little update
i got a pair of 140s and a pair of d8ea s
let me run about a hundred miles then ill pull the plugs out and post the pics
 
I have 145s and no idea what the other jets are I wish I could identify them, I also have the needle in the 3rd notch and the air screw is out 3 turns. I cleaned my carbs in omni au paint thinner took about 20 min a carb, no boiling, and I completely stripped them and soaked them then used white scotch pads since they are very fine and not to abrasive, and gave the parts a light scrub to break up the varnish.

I reassembled the carbs and used vaseline to lube the seals, I then bench set the carbs to sync them, I used a piece of welding wire to hold the first carb valve open then using another piece from the same roll I adjusted the second carb until the wire was just barely able to go between the valve and the body.
 
I have 145s and no idea what the other jets are I wish I could identify them, I also have the needle in the 3rd notch and the air screw is out 3 turns. I cleaned my carbs in omni au paint thinner took about 20 min a carb, no boiling, and I completely stripped them and soaked them then used white scotch pads since they are very fine and not to abrasive, and gave the parts a light scrub to break up the varnish.

I reassembled the carbs and used vaseline to lube the seals, I then bench set the carbs to sync them, I used a piece of welding wire to hold the first carb valve open then using another piece from the same roll I adjusted the second carb until the wire was just barely able to go between the valve and the body.

im not so sure about the thinner thing.. i cleaned mine with supertech (walmart brand) crab cleaner..
do u have any pics with your plugs?
 
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