I just purchased a dynojet kit # 8121 for my 2005 Harley twin cam from HD. My bike is new with no modifications except the screaming eagle air box and exhaust which I just put on.

Please help me with these two questions:

· The instructions state that for an after market exhaust and air box to use a # 185 jet. My Harley is stock with a #190 jet. Do I jet down with the Dyno kit or keep the stock #190 or what ?
· I also notice that there is no slow speed/Idle jet size change. My stock jet is a # 45, will the adjustment be enough for the bike not to run lean or do I have to change this jet to a larger size.

I would appreciate any information you can give me. Do I just install the kit as-is or what? Again my twin cam is stock except for the air box and exhaust.

Thanks,

Dick

 

Not sure wheather the Dynojet has a different sizing designation or not, but a 190 seems big to me. In fact, the high jet usually doesn't need to be changed, just the slow. If they are not furnishing a slow they must have a needle that is tapered to compensate for it. The slow is where a lot of your riding is done, and is pretty important in my opinion. There is no jet change available for the idle circuit. You get to the idle screw by removing the plug that covers it, then adjust by turning the screw.

For a lot less than the Dynojet Kit, you can get the same results by just re-jetting yourself.

Here's a good formula:

1 size larger slow jet, maybe 1 size larger high jet. Run it you might not need it.1988 1200 Sportster needle (the 1988 did not have an accelarator pump, so the needle is different,
cut two coils off of the slide return spring, unplug the idle screw cover, and adjust to get the best idle. (usually 2 to 2 1/2 turns out from all the way in. If you already have a 190 high jet, you probably don't need to change that curcuit.

Hope this helps.

Regards,

Bill

 

Thanks Bill. It sounds like you have done this before. Makes sense to me. I guess I was confused when there was not a slow speed jet change, but now I understand with the needle change since there is one in the kit.

 

I agree with Bill on the mods

Do a #46 in the low, 190 (stock) in the high, shim the stock main jet needle up with 2 -#4 washers, cutting of the spring optional, DON"T drill the slide vacuum hole , but un cap and adjust the idle mixture to the highest steadiest idle and return the DJ kit, not a lot of guys get great results with them, usually lower MPG

You will not run any better for the cost of a jet and 2 washers, maybe $4-5 total expense

#46 jet can be had here http://www.jpcycles.com/productgroup...ore=All&page=1

Here's a comparison of the DJ needle and others

[IMG]local://upfiles/2318/16D5F9A426054439B884FBA82BDF9B87.jpg[/IMG]

Also this will show you where the different circuits come into play



[IMG]local://upfiles/2318/DD10DC22AB3C4AFD850EB3C1A8596183.gif[/IMG]

 

I rejetted my carb about a month ago. It's a california bike (emissions junk). I had the same stock jets as you do. I went to a 48 slow jet and a 195 main jet. When I started adjusting the carb, at stock setup the screw was only a 1/4 turn out. Went 2 1/2 turns out and just tweaked it a litlle bit in and now she runs great. The only mods on the bike are an air box and exhaust likes yours. Gas mileage also went up. Get about 140 miles before switching over to reserve now. Be careful putting the carb back on, I screwed up the manifold gasket but couldn't tell it was torn. I could not get the bike to run right until I replaced it. Two days of tweaking the carb before I found it. If it idles really high, like 3500 rpm or higher and no matter what adjustments you make to the carb it backfires look at repalcing the manifold gasket. Good luck.

 

Hey it is great to get the input fron people that know what they are talking about. I have one question for SENIOR RIDER. When you say shim the main needle jet up with two washers. do you mean put the 2 washers below or above the e clip on the needle? Exactly where?

 

>>>I have one question for SENIOR RIDER.

I guess that's me from the looks of it? (TCSTD)

Remove the top cover and after you lift out the diaphram and everything that comes out attached to it, the washers go UNDER the lip on the top of the needle, in other words, you are raising up the needle in it's seat by putting the washers under it. OK?

Take a look here http://www.vtwintalk.com/m_65123/tm.htm The washers would be right where the #3 is pointed in the picture on the needle.

Here's a better picture , slide the washers up #3 to the lip on the needle and then reinstall it in the reverse order of removal

[IMG]local://upfiles/2318/574AE6195D8A4A5BAD5696B19A76C2C1.jpg[/IMG]

JUST NOTICED YOU MADE REFERENCE TO AN "E CLIP" You shouldn't have an e clip on there unless it is a DJ needle from the kit. The stockers are a fixed lip on the needle, looks like a nail, YOU SURE ABOUT THAT? DON"T mix and match parts with the DJ kit, use the stock needle for this operation.

 

Just for clarification on dynojet's, they are a little confusing. First time I used a kit, the main was smaller size than stock, I called them and the tech explained after some probing that their jets are tapered, they actually flow more than a stock jet even though they are sized by a smaller number. Their jets are just fine and I have put several kits in with good results.



John TN

 

Thanks John,

You are corrct. I called them and they explained it as you did.

 

If indeed they are tapered, one question comes to mind here

If the reference number they use for the jet is the larger taper or the small end of the taper, if it is the smaller taper, then it IS a smaller jet size, if it is the larger end of the taper , then the smaller end ir REALLY smaller then. I wonder about this as they seem to use more gas.

IMO, a taper would make little sense being that it will only flow as much as the smaller diameter ( orifice)
I think what it may come down to here is a smaller jet size , BUT with a rapid taper on the needle so you have a proper idle but with a rapid ramping of the fuel as you lift the needle, I think this comparison will bear that out.

[IMG]local://upfiles/2318/252337748BAE4842A066F75C0ACB0E86.jpg[/IMG]