Posts made by HOTSHOT III

@UngeMan Also worth getting some Bark Busters or similar wraparound handguards as they protect levers/master cylinders as well.

@SpookDog Last time I checked the seals, top bushes and dust seals/circlips were all available genuine from Fowlers etc.

Thanks for the heads up on the lower bushes!!

@SpookDog As far as I know the DTRe internals are the same as the DTR.

I got some XT600 3AJ springs off eBay for mine which solved the bottoming out nicely along with 500ml of 15W oil per leg. But be warned I had to increase the preload on my YSS shock by about 16mm over the stock setting and run the rebound damping on position 29 out of 30 to match the forks so not sure what effect these springs/oil would have in combination with a stock rear shock.

I weigh 150lbs and after this mod the bike jumped better than the stock 2020 KTM 250EXC TPI I had at the same time but TBH the front was maybe a little too stiff; to get it just right I'd like to try cutting 10mm at a time off the spring spacers (if I can get hold of a spare set).

@SpookDog Surface area of a circle is pi (3.142 approx.) x (radius squared). Radius = diameter/2 so for a 28mm carb (14 x 14 = 196), x 3.142 = 615.75 square mm. If you have a barrel that's had loads of rebores you can also accurately calculate its cc (or swept volume) using this method, then multiplying by the stroke.

Surface area of the reeds when fully open is a little more tricky as the fully open reed petal produces an opening consisting of a rectangular part (at the very end of the petal) and a triangular part (along both sides).

I guess you could take care of the rectangular part by multiplying opening width x 6.8mm x number of petals.

There's also a triangular part to calculate which would (roughly) be 6.8mm x length of the part of the reed petal which actually opens. Then you'd have to divide it by 2 because it's the area of a triangle, or just leave it as it is and treat that figure as the total surface area of the triangular part per reed petal (because there's one of these down each side). Still not exact because the reed stops are curved so I'd iamgine the reed petals would follow their contour when fully open but it would give you an idea.

I think though that your fitting reed stops which are close to the specified height will improve the way the bike runs; opening up reed stops is one of those things people experiment with in their youth to try and make 125s faster (don't ask how I know lol). Rather like the previous owner of mine who fitted a massive main jet, then set the float height too low so it was trying to suck on a fire hose with a half empty float bowl

@Stevie-Wonder Glad your carb rebuild went well.

If you want to pin your PV for test purposes, cut down the shank end of an old 4mm drill bit to about 35mm; this obviously locks the pulley in the open position but can't go anywhere when you put the pulley cover back on.

I keep one of these with the tools I carry on the bike as "get you home" in the event of a PV cable breaking. Just remind yourself to remove it before reconnecting the cables/servo as I think the servo would be powerful enough to wreck its own internal gear train if you switched on the ignition with the PV locked in place like this.

Also have you ever replaced the HT lead? I had a high rpm misfire on my 1990 and it turned out to be this; took about an hour to change so the bike wasn't at operating temperature by the time I put it back together and tested it, but it was STILL noticeably faster/more responsive than before I changed it (I nearly flipped it pulling out of my driveway ).

On the stock coil you can cut off the very top of the plastic case (i.e above where the actual lead fits into it), get the old lead out (it's glued in), then clean up the output and solder on the new lead for a really good connection.

Looks a bit messy as you have to tape it up afterwards and seal with silicone but in practice, usually a better option than a LBS replacement coil as these often have the wrong primary and secondary resistances for specific bikes (and BTW it's also worth measuring these).

@SpookDog I guess you could make a TZR pipe fit but is there a reason you want to?

Also the TZR (2RK) engine is very different to the DTR; much lower compression (I can remember blagging a go on a mate's TZR and thinking it'd blown up when I kicked it over) and the CDI unit is different as well as a few other bits.

Not wishing to shoot down your idea, a lot of lads in Portugal build DTRs with underslung pipes, I'm just curious

@biohazard13 My '93 4BL has always dimmed the headlight when applying the brake and I've been meaning to investigate it although it doesn't appear to do anything any harm.

I fitted the 100/80W bulb before riding it on the road for the 1st time. Would be interesting to see if it still does that with the 45/40W candle they were supplied with when new

@SpookDog The stock charging system is well up to looking after the battery as long as it's working properly (i.e delivering around 13-15 volts at 3000+ rpm).

One of the things I love about the DTR is it has AC lighting so the head/tail lights don't take power from the battery (the stator has a separate charging coil, lighting coil and source coil for the CDI) so you can run a 100/80W headlamp bulb in the stock light unit without flattening the battery.

I went out laning at night with a bunch of KTM guys last year and they commented on how bright my headlight was

@biohazard13 The Motobatt ones are very good, I've used them in DTR and DTRe sizes.

Only problem I had was one I bought off ebay that looked like it had been dropped; seller replaced it for me and it was usable for 12v soldering irons etc for a while but eventually it died.

If you have enough patience for form-filling you can register on Hendler's website so they're covered by warranty as well

@Calum Thanks for keeping the forum going!

@MH-Bikes-N-Bits using a 1/4" drive torque wrench (£20-£30 from a cycle shop) and 1/4" drive universal joint and 12mm socket you can get to all the head nuts with the engine in situ, even the one at the front which is close to the frame.

Alternatively you can remove all the engine mount bolts apart from the swingarm pivot and rotate the whole engine around it a few degrees to improve access (I did this once to replace the O-ring in the steel water pipe without disturbing the waterpump cover as I had reason to believe one of the cover bolts was seized)

@SpookDog I've never re-torqued head nuts after running up to temp. Some might disagree but I've never found it necessary.

@Calum Interesting, what diameter is the caliper piston(s) please? And is there a significant difference in pad area compared to a stock DTR rear caliper? Nice bit of machining BTW

@SpookDog Thanks bud no worries, I've been meaning to take a look at this for a while as front calipers are a lot easier to get hold of than rears. And if you can find a suitable master cylinder you'll get the added benefit of a proper dust seal which the stock rear caliper doesn't have!

@SpookDog I had some old front/rear pistons accessible so was able to measure them, stock DTR front is 35mm and rear is 30mm dia. so:

( ((17.5 squared) x 3.142) - ((15 squared) x 3.142) ) / ( ((15 squared) x 3.142) x 100% ) = front caliper has 36.1% more piston area than rear, meaning you need a rear master cylinder which displaces 36% more fluid than the stock 12.7mm bore item to run a front caliper on the rear and retain the rear brake action/feel/pedal travel.
So reversing the master cylinder equation gives us:
(Square root ( (((6.35 squared) x 3.142) x 1.36) / 3.142) )

= New rear m/cyl piston radius

= 7.40mm meaning you’ll need a master cylinder with a bore just under 15mm.

Check by comparing with the stock setup (12.7mm dia. m/cyl and 30mm dia. caliper pistons):

STOCK
((15 squared) x 3.142) / ((6.35 squared) x 3.142) = 5.58 (m/cyl. piston moves 5.58 times the distance of caliper piston because caliper piston has 5.58 times the m/cyl. piston’s area)

FRONT CALIPER AND 14.8MM BORE M/CYL
((17.5 squared) x 3.142) / ((7.4 squared) x 3.142) = 5.59 (m/cyl. piston moves 5.59 times the distance of caliper piston because caliper piston has 5.59 times the m/cyl. piston’s area).

FRONT CALIPER AND 15MM BORE M/CYL
((17.5 squared) x 3.142) / ((7.5 squared) x 3.142) = 5.44 (m/cyl. piston moves 5.44 times the distance of caliper piston because caliper piston has 5.44 times the m/cyl. piston’s area; a 15mm dia. bore m/cyl will slightly reduce brake feel/pedal travel but probably not noticeable. 15mm bore is probably available somewhere).

FRONT CALIPER AND 14MM BORE M/CYL
((17.5 squared) x 3.142) / ((7 squared) x 3.142) = 6.25 so if you run the 14mm bore m/cyl. the rear brake will be noticeably spongy; pedal might hit the frame/footpeg mount before locking the wheel which won’t please the MOT man!

I’ve never tried anything like this and the numbers surprised me so if anyone has anything to add don’t hesitate (checked as best I can but it’s late!). However it does seem logical as anything cylindrical has a big increase in displacement for a small increase in diameter. Hence the twin .50 caliber Brownings in a B-17 tail turret could do a lot more damage than the four .303s fitted to the Lancaster, even though all four .303s had a much higher rate of fire and could pour out a lot more rounds.

@SpookDog said in Front calliper on Rear?...:

@MadGyver

It’s be nice to know which bikes to be looking for! The DTR125 is a 12.7mm piston I think. I’ve found an unknown bike Nissin that looks the same but is 14mm for a reasonable price. Thinking of getting it. The prices on eBay are unfuckin believable! When are these jokers gonna realise that a realistic priced item will sell! Instead of cluttering up the web with overpriced, repeat, repeat, repeat, items that never sell 🤨 All copying the same unrealistic price cause they’re sheeple that’ve seen others do it!...
Pisses me off!...

That might work. ( ((14/2 squared) x 3.142) - ((12.7/2 squared x 3.142) ) / ((12.7/2 squared x 3.142) ) x 100% = 21.5% more fluid displaced when you move the 14mm m/cyl piston the same distance compared to the 12.7mm piston.

What are the diameters of the front and rear DTR caliper pistons please?

@SpookDog Just measured some NIP genuine parts:

Plastic sleeve
Overall length 28mm
ID 12mm
OD 18mm where the roller fits (25mm) 24mm at the "top hat brim" part which is 3mm deep

Foam roller
Overall length 24mm
ID 18mm
OD 35mm

A lot of the ballraced aftermarket rollers look like they're designed to be fitted directly to the frame mount using an M8 bolt (although they don't give dimensions which seems a pretty basic oversight for someone selling universal MX bike parts online); potentially not a problem for the upper DTR roller but to use one as a lower one would necessitate either butchering the stock bracket which bolts to the frame or designing and making a new one

@SpookDog I've always just used genuine ones from Fowlers or Yambits. Worth replacing the plastic sleeve as well. They seem to last pretty well if you degrease and re-lube them when washing the bike or a dash of chain lube whenever you lube the chain.

A lot of MX shops sell aftermarket ballraced chain rollers (basically skateboard wheels) so just a matter of getting one with a 12mm ID the correct width. DirtBikeExpress have a fair selection:

https://www.dirtbikexpress.co.uk/search.php?search=chain+rollers

Yes my top one hardly ever displays signs of use, it's only there to stop the chain slicing through the airbox when the rear suspension is on full compression as you say. In fact when that pic was taken, I'd just swapped the top and bottom rollers as a temporary measure as we were in lockdown! The lower one does a lot more work in normal riding conditions

Here's a copy of a post I did on a DTR FB group a while back showing how to remove the rear suspension relay arm nut (it's a nut which looks like a bolt) which always seizes on the DTR.
Some people chop them out with an angle grinder; this risks damaging the frame if you slip and you'll need to buy/recondition another relay arm which can be expensive.
It's also difficult to beat the nut out because the sidestand bracket is in the way and you can easily damage its internal thread. This method presses the nut out square and you can usually re-use it.

You need:
A length (approx. 160mm) of M6 studding (hi-tensile is tougher than stainless)
M6 nuts or studding connectors (studding connectors in the pics are much deeper and stronger than normal nuts)
A 24mm socket (nut hex is 22mm but the spigot on the frame prevents a 22mm socket from fitting over it squarely)
Loads of different sized M6 washers

First take off the lower chain roller and spray the whole area with WD40 or similar to let it start to work.
Take out the retaining bolt from the chain side and put that and its washer to one side. Find 2 or 3 washers small enough to fit through the hole in the frame but big enough to sit on the end of the nut like in pic 1 (if they disappear inside the nut they'll damage the thread).

Pic 2 shows the brake side. Put the socket over the head of the nut followed by some bigger washers and then the M6 nut.

Start doing up the nut on the brake side (the one on the chain side will disappear inside the relay arm). This pushes on the nut on the chain side, pressing it out square while allowing the head of the nut to move into the socket. Pics 3-6 show why it seizes; even with a grease nipple to lube the bearing, no grease ever reaches the surface where the nut and the bearing's inner race contact each other. Clean these up with wet and dry an make sure you get loads of copper grease in this space when putting it back together!!

If your relay arm doesn't have a grease nipple, now is the time to fit one!! Pic 7 is the original needle roller bearing from my '93 DTR which is still fitted in the bike now and passed an MOT in April 2021. Grease nipples cost pence, drilling and tapping a hole is an easy job for any engineering shop and a grease gun costs £25 on ebay. If you keep greasing the linkage/swingarm bearings they take years to wear out and you'll hardly ever need to take them apart (the 1990 bike I owned in 1992 as a teenager covered over 30,000 miles without my ever needing to do anything to the rear linkage; a big part of what swayed me to choose the DTR as a hobby 30 years later), I do mine every time I wash the bike.

Hope this post helps someone, any questions don't hesitate!!

@Calum Finally sorted as you can see above!!

Turns out on my computer you have to click the download link on a Flickr photo, choose the size you want, THEN copy and paste the URL. Might be because I'm still using the Victorian technology that is Windows 7?

Anyway thanks for your patience