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Auteur Fil de discussion: TW 270 MX EFI - New Project by the Crazy German :-)  (Lu 29546 fois)
macbig2k1
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« le: Mar. 18 Févr. 2014, 10:35:10 »

Salut mes amis,

end of November I've started a new project.
My motocross TW with a 270ccm engine incl. electronic fuel injection.

I've started into the US TW200 a thread about the same topic and here are all of my posts:

24.11.2013 14:08
Hello my friends,

you know, I am a little bit crazy.
I want to inform you about my new project.

 A TW 125 engine converted to 270 ccm into my MX-TW frame.

Some basic facts about the frame/suspension:
- closed loop frame with parts from a Honda CR 250
- front forks/triple tree from a Yamaha YZ426
- front hub from H:One for YZ426/450
- front tyre Metzeler MCE Six Days 110/80-18
- rear suspension from a Yamaha Banshee 350 quad but the the TW spring and a alu spacer to make it fit
- extended swing arm (+ ~5cm/2in.)
- rear tyre Maxxis Bighorn 26 x 9 x 14

And the more important - the engine:
- TW 125 gearing (a bit shorter as the TW 200 gearing)
- 6 disk 5 spring!!!!! clutch from Yamaha IT 175 (many thanks to raptor from the German TW-forum)
- 11/49 transmission with 520 chain (like a 14/62 with 428 chain)
- fuel management by Ecotrons SEFI (Small Engine Fuel Injection) with 34mm throttle body and electronic idle control

-> performance step 1 (249,4 ccm) <-
- 58mm crankshaft
- 74mm piston from Yamaha with 9,5:1 compression
- not modified cylinder head

-> performance step 2 (266,7 ccm) <-
- 62mm crankshaft with a different con rod
(I am not sure about changing to a bigger stroke)
- 74mm piston from Wiseco with 10,5:1 compression
- KPMI valve guides
- KPMI valves with a bigger intake valve (+1 mm)
- KPMI valve springs
- custom made camshaft by WebCam
- optimized combustion chamber
- bigger exhaust port

-> performance step 3 <-
like step 2, but with 11,5:1 compression


I will get in the next 1-3 weeks the last missing parts (crankshaft, cylinder head, SEFI).
Many thanks to randucci for collecting parts and shipping the parts to me.
The frame and swing arm will get in 1...2 weeks a new powder coating.


I'll keep you updated.
Sebastian
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macbig2k1
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #1 le: Mar. 18 Févr. 2014, 10:35:51 »

24.11.2013 18:30
So, here are some pictures (click to get a bigger one):












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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #2 le: Mar. 18 Févr. 2014, 10:36:25 »

26.11.2013 11:22
2,5 years ago I've ordered the XT250 piston plus the timing chain and both sprockets.
I've seen, that the cam shaft sprocket will fit. But the crank shaft sprocket was a problem.
The shaft diameter is 25 mm, but the sprocket diameter is 22 mm.
I was sad about this bad information. And the parts were packed into my "useless parts box".

But last night I've checked the small sprocket again.
The notch for the key is 2,5 mm deep.
In this case it should be possible the inner diameter up to 5 mm bigger -> from 22 to 27 mm.
But I don't need the maximum bore, 25 mm is the must have.



But now I have to make some tests.
Because I don't know how thick the spacer plate can be, for the stroker crankshaft.
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #3 le: Mar. 18 Févr. 2014, 10:37:17 »

30.11.2013 01:18
I don't have a fitting alu plate.
But I have something better: Old cylinder head gaskets!!!!
Every gasket is 1 mm thick, so it's very simple to change the hight.

Today I was able to check the max. hight for all gaskets.
It's only 3 mm!!!!!!
3 mm - 1 mm (head gasket) = 2 mm (cylinder foot gasket incl. spacer plate)



I've checked it with both cam chains (new).
They are very taut.

It's no problem the make the timing chain longer (locks are available), but other facts will make this impossible:
- a 2 link longer chain needs a big spacer plate (5-6 mm) to have a small slack.
- not much space between cylinder head mounting and frame -> modified frame
- big stroke and spacer plate needs a longer rod, a fitting one isn't available
- big stroke and spacer plate with "my" con rod is not possible, because the piston will hit the crank
.....

It would be possible to use the piston and con rod from 2 complete different bikes, but I don't want to make it toooooo extreme.


Before I order the custom made cam, I will modify the cylinder head (big valves) and than I will check the clearance between piston and valves.
And than I will tell WebCam these measurements.

Thanks,
Sebastian

Here are some more pictures:


Original: Distance bearing to sprocket (middle) = 12.5 mm




New: Distance bearing to sprocket (middle) = 9 mm
-> 3.5 mm ring between bearing and sprocket is needed




You can see here, not much space between cylinder head and frame.
Round 2 mm more and it's close impossible to remove the cylinder head.




You can see here the the modified shaft with the reduced diameter to 22 mm.
This is an old crank shaft part.
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #4 le: Mar. 18 Févr. 2014, 10:37:45 »

01.12.2013 23:25
Hmmmm...........
I've found in my storage the 6 speed gearing of an old TT225. I think it's the year 1986/1987.
The gearing of this special year does have the same toothwork/denticulation like the TW (and IT175) clutch boss.

Result:
6 speed gearing plus 6 disk 5 spring clutch
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #5 le: Mar. 18 Févr. 2014, 10:38:23 »

18.02.2014 01:35
Begin January I've received one more US-parcel with some nice parts.
At first a new kick start kit and than a real highlight, because the shown plugs are not available in Europe.
I am sure, these anodized parts will be a nice eye catcher:




My plan was to combine at first the original TW CDI with the ecotrons fuel injection (without using there own CDI), without getting problems with the ignition timing curve.
But now I've made a decision, I will use from the beginning the complete system.
I know, that all TW CDI's (125, 200, 225) are using the same timing curve. I've printed the page with the timing curve out of the TW200 service manuel, changed ignition angle table and saved it into the control unit.

The ecotrons control unit needs input 2 signals:
- pick up coil
- engine start/stop
And it sends 1 output signal:
- spark coil
The easiest way to get/send these signals is to use the original CDI connector. But you can not get it from a normal electronic shop.
I've contacted IgniTech and I will get it in the next 2 days.

It's very important for me, that I don't have to make modifications on the original wiring. I want to keep it stock like it is.
At the moment, the bike is absolutely not street legal. It will be really hard to make it street legal again, because Germany is very restrictive.

Here you can see both cable trees, on the top the fuel injection and on the bottom the TW.
You can see, the cables of the fuel injection are very long, too long. I think, I have to shorten nearly every cable (but better too long as too short).




I hope that I can get  end of this week the modified cylinder head with the new alu intake tube for the throttle body.
I want to get it ready to run soon as possible.
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« Répondre #6 le: Mar. 18 Févr. 2014, 11:33:00 »

Great project ! A little crazy but very cool !

I can't expect the final result  Clin d'oeil
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« Répondre #7 le: Mer. 19 Févr. 2014, 17:52:55 »

Great project ! A little crazy but very cool !

I can't expect the final result  Clin d'oeil
+1  Clin d'oeil hâtes de voir le résultat final  Cool
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« Répondre #8 le: Mar. 25 Févr. 2014, 09:24:35 »

What a crazy project !  Grima&ccedil;ant

Good job ! Good continuation !
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macbig2k1
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #9 le: Sam. 01 Mars 2014, 02:07:59 »

Here are some pictures of the last week.
I am still waiting for my frame, so I've used an other TW for some tests.




The TW is small and there are not much space. My target was to put the battery and the control unit into the battery box. It was very hard to find a small maintenance free battery with enough "cold start power". I have to use a Lithium battery, to solve the problem.
The battery and the control unit fits now perfect into the battery box. A positive side effect, the lithium battery is 2kg lighter as the std. battery (0,5kg instead of 2,5kg).

I had to strip and tape nearly the complete wiring. It was important to bend the wiring loom and than to tape it to make it fit under the side cover.

I've received from IgniTech a new connector like the original CDI-connector.
Now I can use the connector for the following signals:
- power supply for the ignition (new small CDI) - engine start/stop switch
- pick up signal for the ignition (and ground for the pick up coil)
- "ignition spark" to the ignition coil

The control unit needs the engine temperature to calculate the fitting fuel quantity. The sensor has to be placed on the wind protected position. I will use the oil pressure control screw.

The control unit also needs a power on signal (key switch on) for the complete system.
The TW 125 does have a carb heater. I've removed the cable to the heater and the temperature switch. And now I have free "switched plus" (key switch on) connector for the control unit.




In comparison a original wiring loom and the reduced version to the absolute minimum (with only one extra, the e-start)




The new battery is 2 cm smaller as the original battery. It could be, that the fuel pump fits under the seat. A water level was a good help.
I know, there is no space between the pump and the intake. But I will modify the new air box like the old one (third picture). Than there should be enough room for the pump and the fuel lines.




It's not easy to estimate how much room I have between the seat and the air box. To solve this problem I've made a cast/off-print of the seat with many, many, many and many more stripes of paper and thinned glue.




ronnydog has also modified his 5 speed output shaft, to use all 6 gears. But I haven't used a spacer plate, I've grind in a gap and putted in a circlip. And a second gap (like the 6 speed shaft) to lock the 2 gears.


Yesterday I had some time. I've started to assemble the engine (should be 6 pm). I've added piece by piece and than I was surprised, the engine is nearly finished and it's close to 2:30 am.
I had to stop for only one reason, I haven't had a list with the needed screws.

Mid Nov. I've ordered 2 225 crank shafts. I always though, that the crank shafts are identical, but I haven't checked it.
Surprise, surprise, the sprockets for the timing chain are different. The first one does have the same the sprocket like the TW and the second one does have a sprocket for the SC-type-chain.

No question, I've used the crank with the SC-type-sprocket.




The cylinder head before and after the fitting to the 74mm piston.
This is the only modification for this cylinder head. A second head will get the full performance mod.
You can see on the last picture, that I've changed the Aluminum sleeve to a ball bearing. I've made this mod on all of my and customer engines.




I've turned the piston to TDC. You can see, there is a step from cylinder to piston.
This step + a 1mm adapter plate = ~2mm space for a higher stroke
So, there should be enough room for the 62mm stroke crank shaft (+4mm).
-> Maybe I will use a second cylinder foot gasket.




The complete system with installed SC-type-timing chain. I've also mounted a support for the timing chain. The timing chain can not fall down, if I would remove the cylinder head.




The clutch looks absolutely fantastic, like a real racing bike.
Many thanks to my German friend raptor (he has made the first test with an old IT175 clutch).
I've searched a bit in my storage and I've found the push rod of an old DT125. This rod is round about 5mm longer as the original one and it fits perfect.
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #10 le: Jeu. 21 Août 2014, 22:03:00 »

Hi @all,

I have made a decision.
I've canceled for now the EFI project.


In the last weeks and months I've worked on many weekends on the adjustment of the EFI.
But I don't have good results.
- no stable idle rpm
- if I turn the throttle and go back to idle position, the engine doesn't go back to the programed idle rpm
-> no working "engine brake" (I hope this 1:1 translation is correct)

Last Saturday I've switched back to my good old Mikuni 28 mm flatside carb (VM28-418) from my TW230 SM.
The engine has started after some hours of working.

In the last days I've worked a bit on the carb setup.
I have 2 needles to work with it.
With the first one the engine runs too rich at 50-75% throttle opening and with the other one the engine is running too lean at the same throttle opening.
I've ordered a new needle and I hope that I get it tomorrow.

I hope that I am able to find a nearly well working setup, because I want to ride on Sunday at the SOC (Saxony Offroad Cup) -> a 3h hard enduro race.


After some tests I have to say, the 250 cc engine is running really well. I think it would be better with a bigger carb, but at the moment I don't have a carb with fits without modifications (plug'n'play).


Something very important, the EFI project haven't ended, it's just deferred to an other time.
Later I want to use the MP25 management unit by KMS.
The only problem, it's very expensive (only for the control unit: 650 EUR without VAT).
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TW125@233ccm(SM) TW125@250ccm(MX) MZ Mastiff660


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« Répondre #11 le: Mar. 26 Août 2014, 21:36:33 »

Hi at all,

Friday and Saturday I've made some test rides on a parking place to find a good carb setup.
The bike is running well.
My air/fuel ratio meter and the rpm display is a huge help to make the adjustments.

The setup is good (not perfect) for low and mid rpm, just over 7,000-8,000 rpm it not so good.

You can not imagine, what for a power the engine have.
You know, to make a wheelie in the 1st gear is no problem with the 125 cc and 200 cc engine. And maybe it's possible to make wheelie in the 2nd gear, with a TW200 and a short transmission.
But......
With this engine it's no problem to lift the front wheel in the 3rd gear!!!!!!!
-> Not just for some meters, I am sure it was minimum 15 meters.


I hope, that I can visit in the next week a small performance tuner shop to make a dyno run (performance chart).

Best regards,
Sebastian
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