DR750 & DR800 owners thread

This spring has been cold and foggy until the very few recent days in my part of the world. So I took my time to continue modifying the Big.

During winter I fit GSXR-1000 exhaust with headpipe made by Lars (inmate Resi).
This of course led to some air filter mods to let the engine breath in, too. What would be the reason to breath out when you can’t breath in, right?
So I cut full triangle auto of air filter intake opening to make it larger and then made a backward facing wind deflector out of plastic bottle and tape just like Ray did.
The bike run very well and pulled strong through the gears to 164kph (on GPS) in the 5th gear. Probably would have gone more if the rider had more guts. No ill affects from strong crosswinds or leg position. Main jets 130, needles raised one notch, pilot jets 45. There was some some popping when decelerating, I guess the mixture was on the leaner side.

I was very happy until I hit an innocent looking water crossing. It was not too deep until the very end. Suddenly I was in deep water and engine died.
Water flooded air filter and wet paper did not let the bike to start again. I spent a lot of time drying the air filter before I could start the bike again, of course running very rich for at least an hour until the paper dried finally.

I took this as a perfect excuse to go for a foam filter. After some measuring and research I decided to copy Stefan’s airbox as I am not so talented making my own design like Ray and Rob here. I told Stefan about my plans by e-mail and he was kind enough to tell that his airbox is an “open source information” and it wouldn’t be a problem if I copy it. I promised to buy Flatslide carbs from him one day...
Bought some aluminum and UNI filter and came up with this (it is still in the middle of process here):


Airbox version 1.1 versus version 2.0:


The whole effort would’ve been useless if it wouldn’t make removing carbs easier. Therefore I decided to relocate all electric stuff and brake fluid reservoir so that nothing is attached to the so called airbox (better call it an air filter shroud).
Voltage regulator in the front under the tank and CDI on the opposite side:


Starter relay, main fuse and indicator relay attached to the frame crossmember.




Clutch, sidestand, decomp switch circuits and their control unit with a lot of useless wires removed. KISS:


Brake fluid reservoir turned around and attached to subframe:


Of course I didn't have place for full size battery. New 8-cell LiFePo4 unit. I have my doubts if it will hold up in cold. We'll see...


Battery wrapped into self amalgamating tape and fixed in place by temporary means (meaning it will stay like this for ever). I bought a crankcase vent filter off ebay but its filtering capabilities were far from sufficient. I desided to make my own out of plastic bottle, some foam and filter oil. I made similar filter out of an old fuel filter for carb vent hose.




Test riding showed that with 130 and also with 132.5 mains the bike does not run when wide open. Hardly pulls to 115kph – 120kph. I tried to pull the cold start enrichener but it did not help significantly. Maybe just a bit. Other than that the bike starts OK and accelerates good from 0 to ½ throttle. Gonna do the Wide Open Throttle test ride and read the spark plugs as soon as time permits.

I managed to test new airbox in deep water crossing, too. After the crossing the bike stalled, and ran very poor after starting again. Removing the seat showed that airbox looked like a half filled bathtub. Drainage hole was blocked by sand and small stones. Draining the water cured the problem and the engine ran again like before. Guess I have to dump the original drainage hose and make bigger holes in the bottom of the box.

mait, you're doing an amazing job with the Big. its a pleasure to read.

coming back to my problems...

started my brother's big with his carbs - everything works great. removed his carbs, and put them in my big. starts fine, feels rich, gives black smoke out of exhaust when giving revs. I don't even have to rev it high, 4k is enough to smoke the underground garage :/ and the fumes are not oil. its petrol.
check the the exhaust header pipe ... it got glowing after a minute of work, i hope the valves are ok ... so to sum up to me it sounded like timing is off mark.

valve head off - and then I was stumbled.

tdc of compression by the mark on rotor:


and the markings on the camshaft look like this:


everything looks proper to me...

now I am thinking back, trying to figure out what I did wrong. the main thought is that I have put an SR43A camshaft there, whilst my bike is an SR43B. to make it work properly I recon I need an SR43A CDI (part no (32900-31D00) ... sounds about right, doesnt it?
Anyone got a spare for sale? did anyone try the slovakian cdi's? are they any good?

SR43A camshaft works in SR43B without issues. You do need to check something else...
Your marks on shaft and camshaft totally OK, this is normal. They shall not line up perfectly.
Idea is that you line them up THEN let tensioner move out and tighten chain which will inevitably cause small offset on camshaft position.

Wundis I agree with Blue, your problem is somewhere else not in camshaft. I have now SR43A camshaft in SR42B and it worked fine when jetting was OK.
The marks do not align perfectly, it has confused many people here before.

Did you use your bro's fuel pump too? May be worth a try.
If the problem persists - take your brother's CDI and give it a try.

Haven't you blocked air filter intake somehow by any chance? Maybe some dirty socks in there restricting airflow.

When you adjust the cam chain tensioner it will move the timing marks .Do they all line up when there is no tension on the timing chain ?

Thanks for the reply. Blues, mait, are you guys sure SR43A cdi would make no difference? Has anyone tried replacing just the camshaft to the non limited version on a SR43B? SR42 is a different story alltogether, your CDI unit is different.

Whilst testing, we used my brothers carb which worked perfectly in his bike prior to our test, with my air filter, my fuel pump (freshly rebuilt with a mikuni pentagon repair kit - works like a charm).

The inlet was definitely not blocked :)

I don't think that a rich mixture could cause both glowing header pipe and smoke out of the exhaust...
I am trying to remain logical, but there aren't that many places that I could have gone wrong. If the CDI would be causing it (i.e. late spark), I would have issues with starting the bike. But it jumps on straight away.
Worn camchain sprockets? Would explain retard timing, but the marks would be off...
Worn camchain? Would explain retard timing, but the marks would be off + it had 1 mm of life left.
Incorrectly put tensioner spring (I don't know if thats even possible)?

As mentioned, the camchain had some life left in it when I was checking it, but it wasn't as tight as I would like to think it should be. Should I be able to push the camchain in or should ir remain bowstring tight?

Wrong type (hot/cold) of plugs? Though these are the same as last year...\

If I exclude the carb there is nothing really left in there that could cause problems like that. Except camshaft timing, CDI unit or loose camchain.
I feel like Dr. House with this riddle of the year...

OK, to be honest I do not remember how I aligned them - with the tensioner off or on. I must inspect this part.
Another tircky bit, if I turn "off" the tensioner, the chain is going to be slack. Obviously. Which side of the chain should I keep tensioned whilst aligning the marks? The right one, since the camshaft turns clockwise?


PS I haven't noticed this on the mainpage, perhaps someone could find this info useful:
This Winderosa Fuel pump repair kit (451457)
Fits: Mikuni Pentagon
Repl: Polaris #3085-176
works like a charm for oem mikuni fuel pump repar kit

What is the optimum engine RPM on the 750 at 100? I am getting new chain and sprockets and will use it for touring. From memory I think it is doing 4300 or 5000 at 100......Was thinking of gearing taller

Mick, 15 /48 is standard and around 4250rpm at 100 depending on the rear tyre you have , I was running 16 tooth fronts for a while on some bikes and found where the bike wants sit,it meant I was speeding a little and not noticing unless looking at the GPS .
Original speedos also read roughly 5klm fast at this speed,
The big will pull ok with a 16 on the long halls , but they are not as good to ride in town you get chain back lash if that's the word .
The chain on SR41 and SR/42 run very close to the frame and if you don,t keep the rev,s up it may touch the frame every now and then using a 16 front.
ring any time.

If the crank is lined up on the mark and the cam shaft is alined ( with the lobs up on TDC )then put the chain on ,then adjust the tensioner , the cam shaft will move as the chain is pulled down as the tension increases if the cam chain is very slack before you adjust the tensioner then it must be replaced .If the timing is out you would bend valves and damage the piston,turn it over using a socket and rachet (anticlockwise i think )

Wundis , has the camshaft been removed or replaced from last year when the bike was running properly or have you removed the cam sprocket and put it back on since last year / we need to know.
I did mention this before and want you to double check please not just say yes its allright check it first, are you 100 percent sure you have the fuel inlet pipe going to the LOWER plastic T piece between the bowls and not the top breather one, they look Identical.

Hey Spen your doing a nice job with your bike , looking really good , If you want a tail light the same as the Dakar bike piss that black plastic off and fit a CT 110 postie bike tail light , original Honda about 100 bucks screws and main base and red lence are all separate part No.
I did spot the same tail light on Ebay for half the price and it was LED I think it was Engand too.sorry about the straps hanging .

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Wundis, according to manual you first align then release tensioner. When doing so you expected to take into account chain slack and pre-adjust camshaft accordingly. Marks will never line up ideally after all released.
As for Wunderosa kit - do not buy it. Buy original mikuni repair kits, available on eBay and online. Wunderosa kits known to have rather bad (for bike) membrane that breaks.

OK spen, noted, will re-check and align the camshaft this way. As the term "slack" is somewhat relative, i'm going to refer to the manual regarding the camchain length - it is 1 mm to limit.

Thanks rob,

Here is what i've done through the winter:
New camshaft
New rockers
New valve seals
New balancer chain
New piston rings
Some bearings, bits and bobs, seals there n there, base and top gaskets
Carb float valves
K&N air filter upgrade
Exhaust sorted out

And yes, the fuel is going where it is supposed to go, I am 100% sure of this. I know what it looks like, and my air vent hose is sitting next to the airbox by the inlet.

Back in 2010 zappa wrote this:

So the lines should be tilted to the front of the engine when the cam chain is a bit worn. From the pic it is visible that mine is tilted to the back of the engine.
It must be related to setting the camshaft incorrectly (my dumb ass may have done it with the tensioner on, or I must have been lining it up with the tensioner on).
I'm not going to be too enthusiastic about it right now, evening will show.

I will keep you guys posted.

Ok bluesman, thanks. Noted.

As for the wunderosa kit... it's a snowmobile kit :) but hey, it's allready in - if it breaks it breaks. The membrane that was inside was a DIY construction, most likely made from a used condom and tears. There was a lot of stuff inside that was not suppposed to be in there...

Mait, terrific your doing a fantastic job, as you know I love air box mods .
You may have now lost to much vacume for the CV carbs to function properly , looking at the foam on the filter it is similar to mine too open and won,t fitler good enough in dusty conditions allthough every pic I think you have posted its all ways been a swamp you ride in over there
I run another foam sock filter over the top on my set up that is similar to yours but with pumpers .
On the same bike I did have the CV carbs earlier and similar box that you just made but ran a smaller same DIA filer, but shorter to give the carbs some vacume the foam itself was 100mm long 115 DIA.
You could wrap some cloth or tape around the filter to reduce the air flow to see if this is an improvement before playing with the main jets.

My DIY extended hand guards. Protection for wind, rain, rocks, roost and wrecks. When coming home from the farm a week ago in 10 degree ( celsius ) I felt an ill wind across my hands. The Barkbuster VIP handguards are great but a bit more protection from the wind and rain would be nice. Barkbuster do sell an extended size handguard called "Storm", but being an el cheapo, I looked through the spares box and found my old stock Suzuki guards. I also believe that it is more socially responsible to re-use where possible; everything should have at least two lives. The Suzuki handguards were already damaged with deep scratches through them; they offer protection from wind and rain only and no protection from rocks, trees or falls. Inspired by a famous RTW traveller, Greg Frazier, who has done a similiar thing on a KLR 650, added them to the VIP handguard and the combination should provide the best of both worlds. The Suzuki guards required a lot of sanding to remove some of the scratches and I cut off the original mounting points with a rotary tool. The black paint was applied to the parts individually first and then another two coats after assembly.

Wundis , thankyou for your answer ok that eliminates 1 thing .
Now I want you to do this for me please align up the mark on the side case and the rotor again as before, with the little cam cog pin showing on the top half above the barrel or cylinder .
If you have done this and it is the same as the before last pic .
Now turn the motor one full revolution 360 degrease and if it isn,t where it was before now retime the cam.

My brake lever extension, hope you guys like it.

Spare bracket from a network switch mount and 6 mm bolts. Works nice but needs better paint as I used cheap chassis paint. I've since stripped back the footpeg hanger, removed the upside "U" guard" and painted it ( and rear rack ) in epoxy enamel. I'll paint the brake lever with epoxy enamel in the next month or so

So just to be sure, you want me to put it on the "real" TDC (of the compression stroke), and rotate the rotor 1 turn (anti clockwise), and after the turn check if the cam sprocket has rotated differently? Did I understand you correctly? Why should it change? I must be not catching something