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I'm gonna break down and do it!

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Okay MX Rob and Jeff at Pro Cycle, I need your input. I've finally made up my mind to do the airbox mod on my DR650 and rejet it. I already have the Two Brothers exhaust and ground header weld. Those are the only mods at this time. The altitude here in Amarillo where I live is right at 3600 ft. I need ya'lls input which jet I should use and clip position. When you indicate clip position, is it from bottom to top as in the third position up from the bottom or is it top to bottom? I already have the DynoJet kit (for a couple of years now), and I've got time and decent weather to do it. I'll also be able to get back on the bike in two or three weeks. My arm seems to be healing up good, and I'm getting my range of motion back slowly (painfully).

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Okay MX Rob and Jeff at Pro Cycle, I need your input. I've finally made up my mind to do the airbox mod on my DR650 and rejet it. I already have the Two Brothers exhaust and ground header weld. Those are the only mods at this time. The altitude here in Amarillo where I live is right at 3600 ft. I need ya'lls input which jet I should use and clip position. When you indicate clip position, is it from bottom to top as in the third position up from the bottom or is it top to bottom? I already have the DynoJet kit (for a couple of years now), and I've got time and decent weather to do it. I'll also be able to get back on the bike in two or three weeks. My arm seems to be healing up good, and I'm getting my range of motion back slowly (painfully).

Awesome, another big DR relieved of asthma. 👍 I think you could easily get away with running the DJ150 or 155 main at your altitude... especially if you tend to go higher than lower from that point. Needle clip position is always counted from the top of the needle down. Kit instructions say 4th clip position... start there and see how the bike responds and then try the 3rd position to see if you lost any snap. You might even get yourself a 1/2mm thick 3mm flat washer and try position 3.5 if you lose response. Make sure to file the washer flat on one side so it will fit up next to the D-shelf in the bottom of the slide without binding the needle. Use Jesse's suggestion of using the OEM needle's white plastic washer as a spacer on top of the DJ needle clip so the spring guide sits level instead of leaning over letting the spring drag on the inside of the slide. (the spacer has to be filed/sanded flat on one side so it sits next to the D-shelf making up for the step... it's goal is to hold the needle firmly in place in the bottom of the slide. I firmly believe the spring dragging on the side of the interior of the slide is one of the contributing factors for riders still suffering surging even with the DJ kit installed. The plastic slide runs inside a plastic track... with some miles on the bike the slide and track get grungy and roughed up. Clean both well with carb or contact cleaner. Use some red scotch brite to polish up the tracks on the slide that contact the track. Any binding here can/will cause surging and poor throttle response. This little extra work made a nice improvement on my BST... and then I chucked it on the bench and installed a real carb.🤣🙂

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Got any illustrations? Especially of where the spacer goes.

Well yeah!

You remove the plastic spacer item 21 and make a needle hold down out of it by filing/sanding one side to fit next to the D-shelf in the carb. Once you lay eyes on it and the D-shelf you'll see the reasoning. It will then go on top of the clip item 20. The shim for doing a 3.5 clip position goes right below the clip item 20. The plastic spacers (21) are generally pretty tight on the stock needle... takes a bit of force to press it off.

0010.Gif

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Thanks Rob. The wind has blown most of south Texas past us for the last three of four days, so I have felt much like opening anything inticate like a carb to all the dirt and sand. Not as bad as the recent dust storm photos from China but bad enough to taste!

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Hey that's my dust and sand, but you can keep it. I had rejetted my carb but while the bike was sitting there waiting for the new shock I decided I'd drill the slide. Piece of cake, put it back together, next day find the spring sitting there...... All better now

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Oops. Yea, part of the Land of Enchantment blew by today. I didn't feel to enchanted though. I don't know where the old saying that March comes in like a lion and goes out like a lamb came from because it bassakwards. Then April comes along and tries to be even windier. The "windy city" of Chicago ain't got nothin' on Amarillo!!!

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Oops. Yea, part of the Land of Enchantment blew by today. I didn't feel to enchanted though. I don't know where the old saying that March comes in like a lion and goes out like a lamb came from because it bassakwards. Then April comes along and tries to be even windier. The "windy city" of Chicago ain't got nothin' on Amarillo!!!

Amarillo ave wind: 12.8 13.8 15.2 15.2 14.5 14.2 12.7 12.0 12.8 12.8 13.0 12.7 13.5

Chicago:11.6 11.4 11.8 11.9 10.5 9.3 8.4 8.2 8.9 10.1 11.1 11.0 10.3

But Cold Bay AK beats them: 17.5 17.9 17.4 17.5 16.2 15.8 15.6 16.2 16.2 16.6 17.5 17.5 16.8

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Thanks barko1 you proved my point. My xray technician told me this past Wednesday that Amarillo ranked number three in the country for average wind speed. He didn't remember Cold Bay, AK, but I can't remember what the other one was. I think Cold Bay was rated at the number one windiest place in the U.S. It sucks or should I say blows to be recognized for that.

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Okay, I've got the carb apart. So it looks like after the mods, the purpose of the plastic spacer is just going to be an alignment device for the needle as it will be on the top above the clip. The only thing holding it in place will be the spring tension, correct? Once, I got the carb tore down, it all came into the light. It really helps to have it apart looking at it while you read Rob's instructions. Like I've said before, I can rebuild a Quadrajet without a problem, but this was my first time inside he Mikuni. I think I'll take pics as I go if anybody is interested just let me know. Of course I've already ripped it off of the bike, so I can't document that. Oh yea, the brass plug over the mixture screw is a helluva plug. It's over a quarter-of-an inch thick! Popped right out with a small self drilling screw though.

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shoot me some pic if u have some??/ im going to be doing the same thing u re w/ dj kit in twm or this wk.. 👍

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Okay, I've got the carb apart. So it looks like after the mods, the purpose of the plastic spacer is just going to be an alignment device for the needle as it will be on the top above the clip. The only thing holding it in place will be the spring tension, correct?

That is correct... Jesse is having you mod the spacer instead of using DJ's silly little not thick enough washer they provide in the kit as a spacer to make up for the D-shelf. The sole purpose is to hold the needle firmly in place at the bottom of the slide. Any variance in needle height, other than it being lifted by the slide, is a variance in jetting and air/fuel ratio. The FCR-MX uses a 5mm hex set screw looking device with a small spring and brass flange that screws into the slide to hold the needle in place. You don't want that thing floating around in your carb in any position it desires. 👍

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Here's the pics I took. I got it back together. It fired right up. However, I may need to make an adjustment as there is now more decel popping and also popping when I snap the throttle closed when revving it in neutral. Ran pretty awesome though. Power wheelies in first without the clutch. The first one was totally unexpected. I carried the front wheel about a foot off the pavement for about twenty yards without realizing it until I started to get crossed up!!!! It was too cool!!!

BST001.jpg,

BST002.jpg,

BST003.jpg,

BST004.jpg,

BST005.jpg,

BST006.jpg,

BST007.jpg,

BST008.jpg,

BST009.jpg,

BST011.jpg,

BST012.jpg,

BST013.jpg

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Decel popping will be a struggle between annoying (decel popping) and evil (an overly rich pilot circuit). You will need to balance the two as best as you can. 👍

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The only problems I had was reinstalling some of the hoses. the crankcase ventilation hose needs to be attached to the airbox before the airbox is bolted back into place and the airhorn is in place. There is enough slack in the hose to allow it to be manipulated and installed before you get the airbox into it's final position. Otherwise there is no room whatsoever to attach it to the nipple on the airbox!!! I also ended ulp with one hose left over. Not sure where it goes. It is about a quarter inch inside diameter. Fuel line and vacuum line are in place and working as proved by test ride. As far as moving the clip to the third position and then placing the half millimeter washer beneath the clip, I cannot help but see how this will only cause a problem with the DJ needle. The grooves in the DJ needle are about the same width and would interfere with the movement of the needle through the washer if the washer became stuck in one of the grooves. Then all you are doing is moving the needle to an even higher position, but with no control on when it happens. I left the washer out and placed the clip in the fourth position. Noticable improvement in performance, but how does the DJ 155 jet compare to the Mikuni 140. I know the DJ needle is a lot more agressive.

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Where did you get the 1/2mm washer? That is not supplied with the kit. The washer DJ supplies is what they expect you to stick on top of the clip instead of what Jesse has you do with the modded plastic spacer. You likely don't need a 3.5 clip position in Texas anyway. But if you wanted any .5 position a 1/2mm washer is fine to use. Remember... the needle does not move around in the slide... at least you hope not... so a 1/2mm washer would line up with the 1mm land between the clip positions. Not a problem... done all the time by tuners.

The other hose you are talking about is likely your float bowl vent hose. There is a fitting sticking out of the right side of your carb near the larger diaphragm vent hose fitting. The vent hose just lays up on top of the air box on the right side.

The difference between the DJ jets and the Mikuni jets are right at 10 numbers give or take a few tenths in the jet range that works in the DR650. A MK140 would end up being a DJ149.3 if they made one.

Here:

Mikuni Dynojet Kit

140... 149.3........150

142.5 152.0

145... 154.7........155

147.5 157.3

150... 160...........160

152.5 162.7

155... 165.3.........165

157.5 168.0

160... 170.7.........170

162.5 173.3

165... 176.0.........175

167.5 178.7.........180

170... 181.3

172.5 184.0.........185

175... 186.7

177.5 189.3.........190

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I've pulled a .5mm washer from my R/C truck spare parts. I don't know what I was thinking. I guess I was trying to over think it. Of course the needle doesn't move inside the slide, or I would have been screwed with the spacer modification as there would have been no way to keep it oriented in the slide. How do I richen up the pilot circuit?

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