DT50 - why cant i go up hills (even very small ones)

[ryanwilki]

Hi,

I passed my CBT today so im now on the road!

But i have a big problem. I struggle to get up hills, or even when the road gopes onto a small uphill slant.

It rides ok and then as soon as i hit a small angle of height it starts to die down and go really slow. So then i down change gear and give it near fulls revs and it does the same thing

The best i can do up a hill is about 20mph max in 2nd gear or something.

Anyway, i got home and thought i might have been losing compression or have very little. So i took the hear off and the nuts on the big long studs were not tight at all (one of which had rusted to the stud and the whole stud came out) . When i took the barrel off, the gasket between the barrel and crankcase was torn in half and the head gasket didnt seem too healthy. Also my piston had black marks down the side of it (under the rings).

I then put it all back together untouched. When i tightened the studs and they were just rounding, the threads on the studs werent great and im hoping its the studs that have rounded and not the actual holes that they go into. WHen i started the bike and revved it i can feel a slight leakage of air that feels to be coming from between the barrel and crankcase but cant be sure.

So ive now ordered gaskets and new studs. Do i need gasket sealant or anything? Its these gaskets:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280558761963&ssPageName=STRK:MEWNX:IT

Is my bike ok to ride at the minute? Bearing in mind that i have to rev it really high to get up hills etc

Thankyou very much for any replies

Ryan.

Iv

[Airhead]

No Ryan it's not rideable like that you will do it no good.

It sounds like it needs new rings and who knows? maybe even a rebore, the black marks are signs of 'Blowby', this happens with worn piston rings or a worn bore. the gaskets will need replacing, be sure not to get any debris into the crank case when removing all traces of the old one, stuff a rag in there while you clean it up.

I am concerned about this rounding...It isnt pulling the stud out of the case is it? I hope not as it would need a thread insert which is no job for an amateur,

[wild foamy]

okay mate, lots of trouble there...

on my DT i could do 30 easy uphill, 20 seems to be a bit low (although i weigh 65kg, about 9.5st )

if the head gasket is knackered or the studs are loose you should be able to hear it blowing from the head (mine worked loose on my DT and when it was cold under full throttle it would occasionally pop), on these little engines it is essential that they are sealed up correctly or else they just wont work correctly, the gasket between the bore and crankcase can be manufactured out of ordinary gasket paper available at any good auto parts store.

the black marks on your piston indicate that it is blowing past the piston rings which is definately not a good thing, best thing i can reccomend is a bore kit change, you can pick them up off ebay for about £40 and it will give you a new bore and piston and is very easy to do

any more questions let me know, i used to have a DT50MX and god i really do miss it

[ryanwilki]

Im pretty sure it has a 60cc big bore kit on (43mm piston) will double check tomoz.

And i ordered standard gaskets. Just realised i will have to send them back (stupid mistake). So what do you think the best option will be? New 60cc big bore kit (ie whole new barrel, piston, rings, gaskets) and then my new studs too

like this one:

http://cgi.ebay.co.uk/YAMAHA-DT50-DT50M-DT50MX-BIG-BORE-BARREL-PISTON-KIT-/220669549503?pt=UK_Motorcycle_Parts&hash=item3360ee1bbf

So if my new studs wont tighten either, what work will i have to have done?

cheers

Ryan

[Airhead]

When i tightened the studs and they were just rounding, the threads on the studs werent great and im hoping its the studs that have rounded and not the actual holes that they go into.............

So if my new studs wont tighten either, what work will i have to have done?

cheers

Ryan

So you said you hoped it was not the actual holes the studs go into

Thats when I thought that maybe as you tightened the nut on the head you would either see the stud pulling up through the nut OR the whole lot would just spin round. Either way this is very bad news and a new thread insert would have to be fitted into the crank case. Like I said it's not a job for an amateur and would mean buying a special insert kit and drill as well. do the threads in the case look good or have they gone?

[ryanwilki]

So you said you hoped it was not the actual holes the studs go into

Thats when I thought that maybe as you tightened the nut on the head you would either see the stud pulling up through the nut OR the whole lot would just spin round. Either way this is very bad news and a new thread insert would have to be fitted into the crank case. Like I said it's not a job for an amateur and would mean buying a special insert kit and drill as well. do the threads in the case look good or have they gone?

They didnt look to bad. Im thinking its more where the nut screws onto the stud at the top as all the thread has been ripped off that bit. But still, the whole stud unscrewed out and the nut is stuck on the top. Some more studs and nuts are on their way now anyway so i'l soon know whether the crankcase needs redrilling and have the insert in (fingers crossed it doesnt)

When i do get the studs, how do i get them screwed into the crankcase, do i just screw them in as far as they will go by hand hand and then slide the barrel etc on top and then put the nuts on top? Or is there a different way?

Thanks, much appreciated.

[Airhead]

When i do get the studs, how do i get them screwed into the crankcase, do i just screw them in as far as they will go by hand hand and then slide the barrel etc on top and then put the nuts on top? Or is there a different way?

Thanks, much appreciated.

First have a look at what they are screwing into, do the threads lookk in good shape? if so breath a sigh of relief.

Next blow into the holes to expel any bits of debris (rag in crankcase mouth)

screw the new studs in by hand until they bottom, then usind vise grips (mole grips) nip them up.

If you havent got any vise grips you can lock two nuts together on the top of the stud and then nip the stud up using the top nut.

Where are you Ryan, why dont you fill in your profile properly?

[ryanwilki]

First have a look at what they are screwing into, do the threads lookk in good shape? if so breath a sigh of relief.

Next blow into the holes to expel any bits of debris (rag in crankcase mouth)

screw the new studs in by hand until they bottom, then usind vise grips (mole grips) nip them up.

If you havent got any vise grips you can lock two nuts together on the top of the stud and then nip the stud up using the top nut.

Where are you Ryan, why dont you fill in your profile properly?

Ok i'l strip it all down tomorow morn and clean off the old gaskets and clean out the threads. Hopefully the threads will be fine. Just to clarify, once ive slid my barrel off my piston and replaced the piston by taking the pin out of the piston (or is it gudgeon ) how do i get my new barrel past my piston rings? Do i need some sort of compressor or can i use something else - preferably free?

I'll get some pictures tomorow of the the whole kit, see what you think.

Oh and my profiles now updated - im in bolton, manchester

thankyou

[Airhead]

Are you replacing the piston?...did I miss something?

Whether you are replacing the piston or rings or both, you you know what size to order?...There may be a number stamped into the piston crown. I dont know if you know this already.

Tip, as you are sliding the barrel off and before the piston exits the bottom of the barrel, thats when you should by habit stuff the rags around the case mouth...just in case the rings are broben and to prvent them or anything else falling in there.

No special tools required, give us a shout when you are ready with the parts

[ryanwilki]

Hi.

Yeah Ive got a 60cc rebore kit on it and my carb is jetted for that so I'm just gonna buy a whole new rebore kit and fit that. I will have piece of mind then that I'm not losing pressure etc.

Just a last question, how long do I run it in for and how should I ride during this time? Also, do i need to use any kind of gasket sealer when im putting it back together?

Cheers

[ryanwilki]

ok ive stripped the whole top end down. The studs came out with a bit of persuasion and ive cleaned the crankcase and head up. Just got to scrape of the reminents of the old gasket and im ready for the new parts to be bolted on.

I measured my piston more accuratley and yep it is 43mm so already has a 60cc bore kit on so i shouldnt have to re-jet my carb because the spark plug was pretty close to chocolate brown before.

here are the pics of it all:

thanks again for your help

[ryanwilki]

Im just about to order a big bore kit from yambits but it doesnt come with gaskets. The seller said they arent included but she sells them separatley in her ebay shop. So i had a look but she only sells standard gaskets, not ones for a 60cc kit. Does it matter if i buy standard or do i need wider 60cc ones??

heres the bore kit for yambits:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=220669549503

and here are the gaskets that i ordered yesterday (when i didnt think about them being different for 60cc or think i needed a new piston/barrel etc) but now im thinking i might have to cancel the order because i ordered standard ones:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280558761963&ssPageName=STRK:MEWNX:IT

sorry for all the questions, i just want to get it all right this time. I will be travelling 10 miles to work everyday so needs to be ok

cheers

[Airhead]

Looks to me like the gasket set you bought is for a watercooled bike, the cylinder you are buying (which is incredibl cheap) is an aircooled jobbie!

So it goes without saying...cancel the gaskets they are no use whatever the bore size is. Wild Foamy is yer man on DT big bores.

[ryanwilki]

Looks to me like the gasket set you bought is for a watercooled bike, the cylinder you are buying (which is incredibl cheap) is an aircooled jobbie!

So it goes without saying...cancel the gaskets they are no use whatever the bore size is. Wild Foamy is yer man on DT big bores.

I just asked yambits whether standard gaskets will work and they said that they will be fine if im using a standard cylinder head, which i am. So i can use standard gaskets. The ones i bought say they are for my bike and the picture is just for illustrational purposes so how come you think they are for watercooled? Im just aking because they were cheaper than the other sets and it would be less hassle if dont have to cancel the order.

Cheers

[Cynic]

I just asked yambits whether standard gaskets will work and they said that they will be fine if im using a standard cylinder head, which i am. So i can use standard gaskets. The ones i bought say they are for my bike and the picture is just for illustrational purposes so how come you think they are for watercooled? Im just aking because they were cheaper than the other sets and it would be less hassle if dont have to cancel the order.

Cheers

Dont worry on the gaskets the example photo is for a water cooled bike thats all, the big bore is just that a bigger bore. The dimentions of the base of the cylinder will be the same as the std unit. The head gasket will have a slightly smaller hole in it, whatever the std bore size is but the piston will never make it that far up the cylinder so it will be fine. If you really want to you could trim the copper slightly but i never botherd when i had a bigbored DT50.

The only shame is that the pukka kits that used to be about are gone, big ports and high compression rings, the top ring on my old 50 was an L shape and reached up the side of the piston by around 4mm, the second ring was a keystone with expander. The kit i had was just as good to look at as use. Cost 70 odd quid back in the late eighties mind. God that old 50 of mine flew.

[ryanwilki]

Dont worry on the gaskets the example photo is for a water cooled bike thats all, the big bore is just that a bigger bore. The dimentions of the base of the cylinder will be the same as the std unit. The head gasket will have a slightly smaller hole in it, whatever the std bore size is but the piston will never make it that far up the cylinder so it will be fine. If you really want to you could trim the copper slightly but i never botherd when i had a bigbored DT50.

The only shame is that the pukka kits that used to be about are gone, big ports and high compression rings, the top ring on my old 50 was an L shape and reached up the side of the piston by around 4mm, the second ring was a keystone with expander. The kit i had was just as good to look at as use. Cost 70 odd quid back in the late eighties mind. God that old 50 of mine flew.

cheers, cant wait to get it all now. Should be here by tuesday so will do it tuesday night. I'l let you know how i get on.

Do i need to lube the barrel up with a bit of 2t oil before i slide my piston in? and does the piston need to go a certain way?

thanks

[Airhead]

cheers, cant wait to get it all now. Should be here by tuesday so will do it tuesday night. I'l let you know how i get on.

Do i need to lube the barrel up with a bit of 2t oil before i slide my piston in? and does the piston need to go a certain way?

thanks

Dont forget to put the base gasket on and seat it properly

Then fit the studs and nip them up, just a nip...dont go mad.

RAGS in the crancase mouth from the very start

Yes the holes in the piston are at the back.

Oil the bore as you said and also the small end bearing before you slide the pin in.

You may find that the rings have a thin crinkly expander ring too...if they do it goes in the bottom groove with the gap around the little peg.

Top and bottom rings are often different so you need to identify which is which before you try fitting them in the grooves. The top one sometimes has a mark etched into it near the gap, it is usually a keystone ring whereas the bottom one is parallel, It is important you are sure of this before attempting to fit them.

Also look out that they go on the right way up so that they go around the pegs ok.

A novice may find it difficult to lower the bore with one hand and manipulate the rings and piston with the other...do this and risk breaking the rings (hence the rags), so get some help lowering the bore over the piston.

[ryanwilki]

ok thanks!! i feel very confident now

[Airhead]

When you first start the bike up, hold the oil pump fully open by turning the pulley by hand for around 30 seconds...dont forget the little oil pipe on the inlet manifold. Speaking of which...are two of the corners snapped off ? Thats a bit of a worry, I would use some silicone manifold gasket run a bead around the joint, that way you wont have to apply too much strain on those broken corners...just nip them up.

[ryanwilki]

When you first start the bike up, hold the oil pump fully open by turning the pulley by hand for around 30 seconds...dont forget the little oil pipe on the inlet manifold. Speaking of which...are two of the corners snapped off ? Thats a bit of a worry, I would use some silicone manifold gasket run a bead around the joint, that way you wont have to apply too much strain on those broken corners...just nip them up.

ok will do. Can you suggest any, preferably cheap. The gasket didnt look great on the inlet manifold so will be replacing that and then do as you suggested and put gasket sealer on it. I have no idea why the corners are snapped but the screw bolts were really really tight, took me ages to get them undone. Im going to use 10mm bolts to put it all back together, i find it difficult with screws.

I might need a bit of help when putting my piston and rings on properly but we'l cross that bridge when it comes to it. I have a guy at work who used to tune and repair 2 stroke bikes so i could always take the piston in work and get him to help me. but it would mean another day off the road