Mystereid,

My son always tells his buddies that they will have to get up very early to
catch the oldman off guard. Well you got up early alright. So I will add
more info to address the right spring selection.
All factory springs appear to be made out of .032 spring wire.
2000/2001 had a pitch of .140P and were 26/27 coils. Length 3 5/8”
New 2005 has a pitch of .120P and are 26/27 coils. Length 3 1/8”
When we cut the old springs 3-4 coils, we had a length of 3 to 3 1/16”
When you tests the force of the cut old spring to the 05 spring you get
very similar gram forces throughout compression.
Summary:
If you check your spring and it is 3 1/8” with 26/27 coils, this is OK.
If you check your spring and it is 3 1/8” with 24 or less coils,
order the new 05 spring.
If your spring is over 3 1/8” long and has 26/27 coils, cut to 3 1/16” to 3 1/8”.

Thanks Mystereid for noting that this could be a problem. If I missed something else,
please let me know.
OMR

 

First of all killer thread Oldmanracing, I've been following this one since the original post. Question, will these carb mods work on a carb with no air box. I relocated my battery up under my seat, so I have no air box. I know I am missing out on some top end power, but my plan was to get a new carb soon. Its probably not going to happen this season, so in the meantime I wanted to mess around with some of your mods. Specifically the mods to the slide, spring, and balance tube.

 

FatHolly,

Because my son cannot race without a airbox(Stock Class Requirements), I have not done any testing without one. Lid off has not been good.
Many of us tryed the direst mount filter years ago and it had its benefits, but physically it was a mess.
The total removal of the airbox was MRHP's design and I think that you may find that with my Stock Carb Mods and removed airbox, you may be very successfull.
Air tumbling into the airbox is eliminated from the equation.
I have purchased a part to see if I can contain reversion in the intake manifold, thus maintain inertia
and not cause the slide to flutter at high rpm's, with lidoff. If this works with lid off, it will also improve
performance with airbox removed.
Start your mods and when I receive and test this new part, I will let you know my results.
The part sells for about $20. Let me know how you are progressing.
OMR

 

What riding today, first time since doing the carb mods oldmanracing described in this past. It ran better than perfect. I runs better in every way than before.



Thanks,

 

Thought I would update my results.

Got my DJ jet kit last week, started testing on Saturday.

Step 1 - Put the DJ needle in, 2nd position from the top. Left rest of jetting the same, 175 mikuni main, airbox lid off. Improved midrange response over the stock needle in the richest position.

Step 2 - Adjusted the needle to the 3rd position from the top. Whoa!! Totally changed the midrange hit of the powerband. Engine still felt weak on the top end. I have to agree with the rest who said they like DJ needles better.

Step 3 - Increased the mainjet to DJ 190. Top end increased, quad revs hard enough to bounce off the rev limiter in 5th.

Step 4 - Moved needle to 4th position, seemed to bog in the midrange.

Step 5 - Moved needle to 2nd position, did not pull as hard through the midrange as it did in the 3rd. Moved needle back to the 3rd.

My next step will be to increase and decrease mainjet sizes until I find optimum settings.

OMR,

I am still nervous about drilling out the vent holes in the slide and removing the balance tube from the airboot. Looking at the stock set up, the vacuum from the airboot would be what raises the slide. If you remove the tube and increase the size of the holes, could you explain to me what raises the slide? I've sat looking at the slide while it was out with drill in hand, but I just can't grasp the concept that occurs with the change.

 

OMR,

Did a search on past posts of yours and answered my own question, the tube is on the bottom of the bladder. I will be drilling out the holes asap and will order a vent filter as well.

 

Latest Testing Update:
It has been 5 weeks since I have done any testing.
My son put on a new overrev design pipe and we wanted to compare to endcap.
Endcap still has more torque at bottom, but upper mid and top this new pipe ran great.
I wanted to see if we could run better with the lidoff.
It ran better, but could only pull 7600rpm in 5th.
Put the lid back on and it would hit the rev limiter in all gears.
Jetting had a twist. The higher I raised the needle and put in a smaller main,
the better it ran.
Last tests was with the needle in the 6th groove(DG) and a main of 180(DG).
Considering I run a modified emulsion tube that requires 3 sizes larger main to
flow the same as a stock emulsion tube, that would mean a main with stock emulsion
of 165(DG). 165(DG) would be equal to a Mikuni 155. Outside temperature was 55-60.

MrHP told me to try a 145-150 some time back. Endcap I could not get this low.

Conclusion:
Still had best results with lid-on.
Exhaust systems have a direct impact on jetting of a cv type carb.
Use my specs to start, then fine tune, and bigger is not always better.
Try to raise the needle to get more mid range power and lower main to lean out the top.
The aggressive taper of needles used for the DS, have a direct effect on final main jet selection.
Amount of open area around needle jet and main jet size, control final fuel flow.

 

Cammer.

The DS,s I work on here have the mods OldMaracing talks about. I am around 5000ft, give or take, and we use dynojet 185 to 195 with lid on or without. Running anything smaller is going to make the top end very lean. 185 is about minimum you need to start at, even with the lid on and the bigger snorkel to the airbox. With the lid of you need to be around 195 main jet. This jetting will give you a air fuel ratio of around 14:1 maybe a bit less, right accross the RPM range. I normally like to tune the quads to run around 13:1, so the jetting I gave you should be about right for that mixture.

At the coast, the guys are running size 200 main jets.

What you can try if you have not modified the slider yet, by adding the extra holes, is to do the balance tube mod only and run with the lid off.

A guy that tried it, said it made a big difference and gave him some very good power output. He was running no airbox with the stock snorkel and K&N. He struggled to keep up to some modified raptors before the mods, now he keeps up or beats those some raptors. He only did the balance tube mod, and the slider was left stock.

Oldmanracing, when will you have dyno runs of your mods. I need to schedule some time and get a hold of a stock DS to try all the different mods and see what each step adds to the power output. I have never proved to myself how much each mod ads to the power output.

I am a bit baffled why you can hit RPM limit with the lid on, and not with the lid off. On all the dyno runs I have done in 3rd gear, the DS accelerates faster without the lid, than with the lid on. It hits RPM limit in 3rd about 0.3 seconds faster than with the lid on. HP output between lid on and lid off was marginal, with only about 1HP more without the lid, but it got to the limiter quicker.

I want to buy my own dynojet dyno soon, instead of sharing one. Then, I will have all the time in the world to play with it.

 

Well Good Morning or is Evening Freez,
Glad to see you chime in. You don't know how bad I would like to run with lid off.
I thought with new pipe and cooler temps that I would rev better.
From 6500rpm up, the tach slows up and shows signs of hitting flat spots.
Then when in 5th, just runs out of steam at 7600rpm.
We are running a 14 tooth front sprocket, so hitting the rev limiter in 5th should not be a problem.
With lid on, when the motor is turning 5500-6000rpm, it has the effect of a bigger cam kicking in and pulls hard all the way to 8600rpm. I haven't given up, but only have two more tests to do.

I would like to do some dyno's tests, but I was off work for 6 months and now am selling cars.
Auto sales in Wisconsin have reached a major low. This has turned out to be a bad year for me and my family. Like they always say, when you get older and make good money, you are the first to go when times get alittle rough. My wife keeps reminding me that I should of changed careers 15 years ago.

When times get better, I will dyno and share my results.
Check in more offen. Even if we disagree with each other, it forces both of us to think outside the box,
and that is where good changes come from.
Have a great day.

 

Don't get me wrong, I don't mean to say you are of the track with your findings, and you have to do it my way. Dyno is one thing, riding another, so the end results might be different. You are at a much lower altitude, if I remember right, and I am at 5000 ft. Then I ride in very hot conditions and our winters are without snow, so we have a lot of variables between the two of us.

With the stock tyres, sprockets and full pipe, the DS's I work on, hit RPM limit in 5th all the time. It actuall is very bad, with the guys coming back and telling me the bike has a problem…lol. That is until I tell them, you are going much faster and need to start thinking about adding more top end speed top stay of the limiter. To get them of the RPM limit, we tend to go for 22" tyres at the back. This also gives the DS a bit more ground clearance, for technical riding. With the bigger tyres, we stay of the limiter in 5th. It is cheaper than having to fit a new CDI with a higher RPM limit.

Top speed on the DS with these mods are around 80 to 82 miles per hour, checked with a GPS. I had to make a new intake for my raptor to stay with them on top speed…lol

The nice thing with the 22" tyres are the fact that they grow big time at top speed. Riding behind the DS, you can see them grow, adding more top end speed, while having a nice low down gear ratio, to still give good acceleration. Sprockets and smaller tyres tend to hodl thier shape more and you loose out on the growing tyre thing.

A guy in OZ, did the vacuum hose mod only, without the airbox and said it made a massive difference. He did not do the slider mod. It made such a big difference his friends who had the quicker raptors thought he installed a new high compression piston and cam. A 5 min job added the power he needed, and he did not touch the stock Dynojet main and needle jet recommendations. Was running a 200 main jet with stock needle clip position.

I am wondering if the vacuum tube by itself is not a better mod to do 1st, than to drill the extra holes in the slider. If you don’t like, it you can go back to stock, and it would not cost you anything.