DT175

[GSXR988]

Hello to everyone,

My name is Nick and live in West London. I have been riding bikes of all types since 1978 and have just purchased a DT175 for a trip down 'memory lane'.

Because of this purchase I figured I would join this forum for some like-minded people and some helpful advice.

The little Yam was registered in 1979 and has a tubular monoshock swingarm not the box-section item - does that make it an 'E' or an MX?

The previous owner did some restoration/overhaul work; rebore, new headlamp, some new wiring, taper head bearings/wheel bearings, spark plug, engine oil, fork oil, clutch cable, new inner tubes etc. I will put a picture of it on here soon. I intend to strip it down and shot blast/powder coat the frame and swingarm, find original blue mudguards, tail light and get the tank resprayed.

The bike presented me with 2 problems on the ride home to its new residence;

1) Performance was not good between 1/4 to 3/4 throttle opening - this manifested itself in rough and hesitant power delivery. Pottering along very slowly it is ok and when I gave it full acceleration it is also fine, anything in between is not very pleasant. Anybody any ideas?

2) On arriving home I kick-started the bike and the kick start will not return to its normal resting place unless i pull it back by hand or foot. I suspect the return spring has broken - anyone know any better? (update - kickstart has started to behave normally now!).

Any help is most welcome and hopefully I will be able to assist other members on here in the future.

Cheers

Nick

[DirtyDT]

1) Performance was not good between 1/4 to 3/4 throttle opening - this manifested itself in rough and hesitant power delivery. Pottering along very slowly it is ok and when I gave it full acceleration it is also fine, anything in between is not very pleasant. Anybody any ideas?

2) On arriving home I kick-started the bike and the kick start will not return to its normal resting place unless i pull it back by hand or foot. I suspect the return spring has broken - anyone know any better? (update - kickstart has started to behave normally now!).

1) jets in the carb possibly. Lots of DT carb pictures showing the jets on the forum somewhere.

2) return spring, unless it was fouling on something

For starters have a look here LINKY and here LINKY

[Airhead]

To add to what DDT posted

1) Check needle clip position, factory standard is middle notch, any notch lower (raising needle) would do this.

2) Most likely spring but check the rubber boot hasnt split and binding on the brake lever. Also has the spring been fitted wrong I wonder, theres a little nook (or possibly a cranny)in the casing for the end of the spring

[philmountains]

1) jets in the carb possibly. Lots of DT carb pictures showing the jets on the forum somewhere.

2) return spring, unless it was fouling on something

For starters have a look here LINKY and here LINKY

Hi Nick welcome, I joined recently and am also reliving youth "DT175 MX", another bloody competitor for them parts on ebay,only joking.

I have had loads of great advise on this site,think the E was US model, and was supprised it,s an original blue rare, think oldgit,has a blue 1 ? got a blue front guard but not in good nick, the front,s are cheapish to get it,s the back there are bloody dear WHY ? they are only made form the same stuff they make buckets out OF LOL. the kickshaft well the spring might not have snapped the stubby end might have though ! it sits in a small cavity in the casing, I think this is common and again not dear to sort out.

All the best

Phil

[GSXR988]

Many thanks for the welcome and the advice. Thanks DDT for the links.

The kickstart is working correctly so that is a bit of a mystery! Bike was running hideously today so will pull the carb apart and check needle setting, float height, float needle for wear and jet sizes etc. Will also check spark plug for colour/gap/type/spark etc.

The bike has had a top-end rebuild but unless I am just being paranoid it sounds like it has a small-end rattle or the beginning of one.......which leads me to an article in the Haynes (yuk, don't like Haynes) manual that says if the oil pump is not bled correctly it will give symptoms in performance like I am getting....is it worth bleeding or would it have blown-up by now?

Thanks again.

p.s. In restoration (I am new to this area of biking - I normally wear them out!) is it acceptable to use new bits i.e. nuts bolts etc or should you use genuine old ones albeit cleaned up? I know some people get really anal about these things!

Cheers Nick

[Airhead]

Many thanks for the welcome and the advice. Thanks DDT for the links.

The kickstart is working correctly so that is a bit of a mystery! Bike was running hideously today so will pull the carb apart and check needle setting, float height, float needle for wear and jet sizes etc. Will also check spark plug for colour/gap/type/spark etc.

The bike has had a top-end rebuild but unless I am just being paranoid it sounds like it has a small-end rattle or the beginning of one.......which leads me to an article in the Haynes (yuk, don't like Haynes) manual that says if the oil pump is not bled correctly it will give symptoms in performance like I am getting....is it worth bleeding or would it have blown-up by now?

Thanks again.

p.s. In restoration (I am new to this area of biking - I normally wear them out!) is it acceptable to use new bits i.e. nuts bolts etc or should you use genuine old ones albeit cleaned up? I know some people get really anal about these things!

Cheers Nick

Its always worthwhile to bleed the pump, after all said and done its just removing a screw for a few seconds. As for restoration, you can be the judge of new or cleaned but cleaned wont look like new, however new wont stay new forever...decisions decisions.

The word 'RESTORATION' it's a bit of a mis-noma when parts are replaced by new parts dont you think?

[DirtyDT]

Its always worthwhile to bleed the pump, after all said and done its just removing a screw for a few seconds. As for restoration, you can be the judge of new or cleaned but cleaned wont look like new, however new wont stay new forever...decisions decisions.

The word 'RESTORATION' it's a bit of a mis-noma when parts are replaced by new parts dont you think?

Providing the screw isn't mangled. Easy to do though.

OG posted a thread on the forum somewhere with different bolts etc which can give you a decent compromise between old and new.

[chrisp]

Its always worthwhile to bleed the pump, after all said and done its just removing a screw for a few seconds. As for restoration, you can be the judge of new or cleaned but cleaned wont look like new, however new wont stay new forever...decisions decisions.

The word 'RESTORATION' it's a bit of a mis-noma when parts are replaced by new parts dont you think?

Agreed! my dt250 DT3, because of the state it was in (see my post) is more of a recreation than restoration. I'd estimate more than 90% of the parts used are NOS but i will definitely ride it and use as intended, i'm not precious about it at all. I'm not going to be trailering it to shows in a heated van with carpet, it'll be ridden with muck and dirt wiped off if appropriate!

[GSXR988]

Oh, 2 more things......any recommendations with regard to 2-stroke oil? I believe it is running on Silkolene Super 2 injector synthetic.

Secondly, regarding the poor running....it feels almost like piston slap before it gets into the power band. That can't be so surely as it had a rebore and piston/rings/small end not 200 miles ago......

[Cynic]

Noise like little end wear and feel of piston slap, thats 'pinking', pre-ignition or detonation choose your favorite name..

She's either lean or has something awry in the ig. Could be as simple as a dicky plug.

[JoeWannaB]

Hi Nick,

I'm new to this forum and very new to restoring old bikes so this my not be helpful but I thought I should post up my experience in case it may help you. I have a DT 175A not the MX but I am having a similar experience to yours in regards to the bike not accelerating well in the mid to upper range. Mine idles beautifully and it will rev smoothly all the way to the redline without a hiccup while in neutral or with the clutch lever in. It usually runs pretty well up to about 4000-5000 rpms when under a load but after that, it bogs down. I adjusted the float level, checked the needle clip, set the timing, checked spark plug gap, completely cleaned out the gas tank, petcock and took the carb apart for a thourough cleaning. Each step of the way, I thought I had found the solution only to put it back together and have the exact same results. I was really banging my head against the wall. During my third time inside the carb, I managed to break the float and so I went to the internet in search of a replacement. While I was ordering the float, I decided to go ahead and order a new main jet, pilot jet, needle valve set and a few gaskets to perform a complete carb overhaul. As I was closely examining all the parts to determine if they needed replacement, I discovered that the O-ring that attaches to the bottom of the main nozzle was missing. It is my understanding that this O-ring makes a seal between the main Nozzle and the opening in the float bowl. If there isn't a seal, then gas can flow freely around the main nozzle. When the throttle is cracked wide open, a flood of gas is sucked into the mixture momentarily flooding the bike. At least that is my theory. I won't know for sure if this is what my problem is until my parts come in but it is the only "smoking gun" I have left. If this isn't helpful, I hope it is at least a good story. Good luck and let us know how you fix your problem. Joe

[GSXR988]

Thanks Cynic, the small-end rattle seems to be in neutral and as the engine starts to slow after blipping the throttle - if you know what I mean?

Thanks Joe, my main problem is from very low revs to 5000 rpm. From 5000 rpm it goes fine. It really is rough from 2000 - 5000 rpm.

I took the carb apart and measured the float height. This came out at 16mm. The stupid haynes manual doesn't even mention float height so found it on a link supplied by DDT. That suggested it should be 21mm. I adjusted accordingly but whilst inspecting the float needle it seemed like the sprung-loaded part had lost most of its spring so it wouldn't support the float. I put the carb back on and was not surprised to see petrol coming out of the overflow. I have ordered a new float needle and hope that should fix the float height/overflow problem. Whilst doing this I drained some fuel from the tank and noticed droplets of water in it. I drained a litre of the fuel out until no more water was present. I had a full tank so didn't want to waste it all. I will fit a fuel filter and keep my eye on it.

While the carb is out next time I will check the o-ring situation as you mentioned.

Cheers Nick

[GSXR988]

Oh, one other thing; I replaced the metal reed valves with fibre ones. Good idea or bad? I noticed on both the fibre and the metal ones (before I took them off) that they didn't sit flush with the block at one end i.e. the narrow end of the 'V' (or the bottom of the V if you like). Is this normal? I am trying to recall my 1980 RD200 and seem to think this is wrong. Also, the curved bits of metal which hold the reeds in place seemed to be bent to different degrees especially on one side - this also doesn't seem right. Can anyone confirm these things?

Thanks in advance

Nick

[Cynic]

Sounds like the reed blosk work was worthwhile, metal/fibre, maybe make a difference on an rd500 but a low tune 175 single. Maybe a little.

The little end bearing sounds likely esp as pinking only occuers under load.

Float height......... Can be a pain in the arse to get right. Firstly the float needle isn't suppost to support the floats with that little spring it stops the floats applying too much presure to the tiny valve sealing area.

The float height is measured with the carb upside down, with the float bowl removed hold the float untill it is just touching the float needle. The base (top at the mo)of the float should be 21+_1mm from the gasket face of the carb (without the gasket)

[GSXR988]

Thanks Cynic, but to my recollection the float needle spring should hold the weight of the float when inverted and checking height. The new float needle does anyway and the old one didn't. I will see if it makes a difference when properly put back together.

Anyone any ideas regarding the tangs being at different angles on the reed block?

[GSXR988]

Ok,

Managed to find out from Yamaha uk that it is an MX. Also pulled the carb apart and replaced the float needle, set float height at 21mm, cleaned all jets and nozzles and airways - found the pilot jet to be blocked. I also bent the reed tangs back to their correct positions after finding the specs on-line. After refitting carb the bike felt tons better but then started running poorly again. Stripped carb and found pilot jet blocked again. Cleaned and then fitted in-line fuel filter. Ran really well and felt like it should do.

After a heavy rain storm bike wouldn't start. Checked plug and it was covered in water! I drained the carb and the bike started and was ok again. I couldnt see any water in the fuel filter though. Can it get through the filter paper? This problem happened again after another rain storm. How is the water gaining entry? The fuel cap seems a mighty good fit.

The kick start problem has come back and I have noticed that the kickstart lever stays down when it is used to kickstart the engine when it is hot but always springs back with a cold engine!! Any ideas?

I am having big problems trying to find original blue front and rear mudguards - can anyone help? They don't need to be immaculate but in reasonable condition. My side panels are a bit messy too so if anyone has any knocking around it might be worth a shout.

I got a quote to shot blast and powder coat the frame/swingarm - £120 - sound ok?

Finally, anyone know where I can get a reasonable tank respray done for a reasonable sum?

[philmountains]

Ok,

Managed to find out from Yamaha uk that it is an MX. Also pulled the carb apart and replaced the float needle, set float height at 21mm, cleaned all jets and nozzles and airways - found the pilot jet to be blocked. I also bent the reed tangs back to their correct positions after finding the specs on-line. After refitting carb the bike felt tons better but then started running poorly again. Stripped carb and found pilot jet blocked again. Cleaned and then fitted in-line fuel filter. Ran really well and felt like it should do.

After a heavy rain storm bike wouldn't start. Checked plug and it was covered in water! I drained the carb and the bike started and was ok again. I couldnt see any water in the fuel filter though. Can it get through the filter paper? This problem happened again after another rain storm. How is the water gaining entry? The fuel cap seems a mighty good fit.

The kick start problem has come back and I have noticed that the kickstart lever stays down when it is used to kickstart the engine when it is hot but always springs back with a cold engine!! Any ideas?

I am having big problems trying to find original blue front and rear mudguards - can anyone help? They don't need to be immaculate but in reasonable condition. My side panels are a bit messy too so if anyone has any knocking around it might be worth a shout.

I got a quote to shot blast and powder coat the frame/swingarm - £120 - sound ok?

Finally, anyone know where I can get a reasonable tank respray done for a reasonable sum?

Re Kickstart prob have you had side case off yet as think I might have mentioned before the coil spring has a smaal nib which fits into a hole at the side of cover bolt if this is bust this would be your prob as for ok when cold well could this be down to expansion/contraction spring sticking in right place when cold ? .

Respray why not have a go yourself ,I am going to give it ago with celulose !! have a look at Nevs DTr rebuild for a great spay booth ! he must have a very understanding misis

[Airhead]

..........I am having big problems trying to find original blue front and rear mudguards - can anyone help? They don't need to be immaculate but in reasonable condition. My side panels are a bit messy too so if anyone has any knocking around it might be worth a shout.

I got a quote to shot blast and powder coat the frame/swingarm - £120 - sound ok?

Finally, anyone know where I can get a reasonable tank respray done for a reasonable sum?

Why not have a go at painting the plastics yourself, blue ones are hard to find...mine's blue so i know.

[GSXR988]

Why not have a go at painting the plastics yourself, blue ones are hard to find...mine's blue so i know.

Surely if you paint the plastics the paint will just chip off or am I talking rubbish? They are injection moulded the right colour rather than being painted no?

[Airhead]

Surely if you paint the plastics the paint will just chip off or am I talking rubbish? They are injection moulded the right colour rather than being painted no?

yes they are self colured from new but after 32 years they wont look like new, in the end if you want them to look smart you will have to paint them and do your best not to chip them. you can get primer suitable for plastics.

heres mine after painting