@SpookDog I really don't think an o ring will solve your problems. Your problem almost certainly lies within the cooling system. Sticking/seized thermostat, defective water pump or defective pressure cap. You can easily eliminate the water pump by removing the hose and check if it's pumping and the thermostat by removing it and put in a pan of water on the hob and check the water temperature when you see it open.
@Stevie-Wonder the air screw only affects the pilot circuit so not that. You screw it out to allow more air. Check the float needle seat that it's seating correctly and the rubber isn't perished or missing because that would cause fuel to leak out of the overflow. Notice the little rubber tip.
https://www.ebay.co.uk/itm/194220758338?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=dpDE_KyJTQ-&sssrc=2349624&ssuid=7ztfcrwyt6w&var=&widget_ver=artemis&media=COPY
@89dt125nick hi nick, I used to have a 88 model, the early ones didn't have a servo as this was the learner legal restriction. Later ones had working powervalve but restricted elsewhere. If you remove the powervalve cover on the right hand side of the engine you'll see a small metal dowel which locks the valve in place, you can only move it 180 degrees due to the dowel so either fully open or fully closed. In short open for high end power and closed for low end power so each one is a sacrifice of the other. You can easily retro fit a servo for the best if both worlds but for the older models as you have I believe you need the 3 wire servo as opposed to the later 5 wire.
@Calum I didn't think of that I'm sure they must be raking it as you said but surely in this exceptional case that has affected and touched pretty much the whole world they could do their bit and reduce their commission assuming that is how it works. Apparently he spent 3 years as a POW and he's an ex motorcycle racer. He was in the army endurance racing team and he also set up a motorcycle training school for the army. Visordown did a piece on him I was reading this morning. Captain Tom. What an exceptional man!
@tim85 on my bike they are overflow/breather pipes as they connect to nothing, just directed downwards. I think The smaller lower one is for when you drain the float bowl. The carb warming pipes are on the other side and a bit higher. Sort of directly behind the choke linkage, 2 pipes quite close together and pointing upwards My warming pipes have just been removed and looped at the cylinder head by the previous owner. I guess they're only needed if you live in a cold country.
@shanedalton no you most certainly can not. Use 2 stroke oil to mix with the petrol and make sure that it's compatible for premix as some are specifically designed for autolube/oil injection pump only and they won't break down and mix properly. If in doubt as to the ratio use an online premix calculater. As for the engine/gearbox use either silkolene or putoline light gear oil. It's all very critical as if you get it wrong you'll be looking for an engine rebuild very soon.
@shortstockevs if you are on Facebook join the group 'Frankies French imports'. There's a few guys on there that rebuild DT125LC's who will gladly help you. And you can scroll back through all the posts for lots of pictures during the builds. You may find the help you need on this forum but it is mainly for the later DT125R.
@Scootjockey 37f is dt200lc. Here's another good Yamaha parts supplier.
https://www.bike-parts-yam.com/
@Calum I understand what you're saying about the exhaust wrap, that also came already on the bike, I may take it off. As for the CDI it might have been changed already as it's a 3rm-30 which I'm led to believe is good also quite rare is it not? Also I might add the log book says first registered in the UK 2007 I was told it's a French import.
It has the Athena 170 bore kit, not what I would have chose especially after reading @Calum's opinion on them about port timing etc but it was on it when I bought it. So was the nice shiny new full dep exhaust though not sure how long the front part will stay that shiny as I gather from what I've read on this forum they rust easily. Does anyone here know of anything that can coat/treat it to slow down the rust?
A few things on my to do list eg. Get the powervalve working as the servo is disconnected and it's set fully open, I've bought a battery as it didn't have one so I'll fit that and look at connecting ypvs back up. Also I must look at the jetting as it currently has a 290 which I thought seems a little big? Anybody here used a 290? Any thoughts please? It's a 2000 model.
@Stevie-Wonder "all the photos are now gone"
He changed his YouTube channel name when he built the cb750 but here's the link to his video which is a montage of all the photos of the conversion.
https://youtu.be/uVk7RZRvxDg
@Calum ah yes, before the carb won't make much difference. My airbox is deleted and have a ram air pod filter. Just up couple of sizes on the jets. Some people run no air filter.
@Stevie-Wonder a lean condition seriously affects the temperature. A main jet 1 or 2 sizes too small can easily make a difference of 20 degrees so an air leak caused by a split rubber can be catastrophic.
@SpookDog I really don't think an o ring will solve your problems. Your problem almost certainly lies within the cooling system. Sticking/seized thermostat, defective water pump or defective pressure cap. You can easily eliminate the water pump by removing the hose and check if it's pumping and the thermostat by removing it and put in a pan of water on the hob and check the water temperature when you see it open.
@SpookDog for some reason I thought you knew to use original or Athena. Can't comment on vertex but I've always been of the belief that only genuine or Athena will do.
@Stevie-Wonder good price that, myself and a few others advised you of the float valve a while back. And yes he's right about the screwdriver, that's what I use just have to cut the red plastic sleeve off with a Stanley knife. There's a special pilot jet screwdriver available but it's £30.
https://www.ebay.co.uk/itm/374176786046?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=4ytB3dNFSrS&sssrc=2349624&ssuid=7ztfcrwyt6w&var=&widget_ver=artemis&media=COPY
@Stevie-Wonder yes very good magazine. As is practical sports bikes.
@Calum thanks for sorting it. I was worried for a while there I've been checking in a couple of times a day. It really doesn't bare thinking about to lose all of this information.