DAMN ENGINES!!! advice/help needed

[noidea]

ok

Tonight was a very shit night in the progress of my porting job. I had assumed that the head off the ducar i recently bought would fit on my current loncin engine. Assumption was made on the terms that both heads had very similar structural designs, despite differences in valve sizes and cam gear and combustion chamber volume.

But the ducar head isnt going to fit the loncin barrel/piston.

easy you say, swap the barrel and piston from the ducar over. Nup, the ducar gudgeon is 14mm and the loncin 13mm. At this stage i was about to jump in my car (neither of the bikes working) and drive off a cliff!

Ok, so as far as i can see ive got 4 options, two crap and two wishful thinking.

#1- ditch the ducar head and start work on the loncin head. Yes i would do this but here is a comparison between the heads

Ducar head -Intake- Valve: 27mm
Inside Seat: 23mm
Manifold end of port: 29mm
Manifold: 22mm

-Exhaust- Valve: 22mm
Seat: 20mm
Pipe end: 24mm

Loncin Head -Intake- Valve: 23mm
Seat: 19mm
Manifold end: 21mm
Manifold: 24mm

-Exhaust- Valve: 20mm
Seat: 17mm
Pipe end: 20mm

So the ducar, has much bigger valves, and valve seats. I have also spent a fair bit of time working on this head... it is about 1/2 done atm. The loncin head how ever does have less volume (higher compression) but the valves are tiny, and the seats aswell. The seat is about 4mm smaller than the port so theres a massive lip!

Im pretty keen not to work on the loncin head, so im keeping it as a last resort.

#3- Try and get the seats from the ducar head put into the loncin. This would require a fair bit of work to the head as the combustion chamber design is quite different. Again a last resort...

#2- The Conrod bearings on the crankshaft is the same on both engines. I could tear down both and swap conrods, then put the barrel, piston and head from the ducar on the loncin crankcase/gearbox. Now you ask why not use the ducar? It has electric start, will all the wiring butchered, and several cracks in the crankcase.

#3- Source a piston, 53mm which will take a 13mm gudgeon pin. The ducar piston is 53mm but takes a 14mm gudgeon pin, the loncin conrod takes a 13mm gudgeon. This option would mean i could run the ducar piston, barrel on the loncin which in my mind is the easiest option.

So, what do you guyz think... is there any option i have overlooked in my rage lol.

KEEP YOUR EYES PEELED FOR A 53mm PISTON WITH 13mm GUDGEON PIN!

cheers
Edward

 

[Mack]

There is no easy option in this case. First we need more info. Are the stud spacings different? Measure each one cause some may be right but a couple different. I suspect they are. Also the height of the cylinders. Therefore the length of rods.

 

[noidea]

Yea, havent measured that stuff yet... dont really want to know. But carter has a 53mm piston that will take a 13mm gudgeon for me. So time to see if the barrel/head off the ducar will suite the studs... (fingers crossed!!!!!)


EDIT:
The barrel off the ducar isnt going to fit the loncin, and the head is going to need some milling if its going to fit aswell.

So, how bout that small port theory lol. Looks like i will be velocity porting the loncin head...

What do you think is the theory behind the tiny valve's and seats on the loncin head? Is there anything i can work with or should i see about milling out the ducar head and getting a high compression piston?

To make the ducar head fit im going to have to bring all the stud hole in about 1/2mm and possibly machine the rocker shafts down 1mm. Which isnt such a hassel. Ill just chuck the head on the drill press and the rocker shafts on the lathe. But its the loss in compression im worried about. The head volume of the ducar is alot less, this is compensated by a larger domed piston that has valve reliefs. That piston how ever isnt going to fit my barrel or con rod. So I am going to have to go with a high compression piston, 52mm that takes a 13mm gudgeon pin. It seems the loncin has a larger stroke to counteract the smaller bore size, so then is the piston going to hit the valves?

But maybe the gains with the larger valves and seats of the ducar arent going to make much difference with the stock cam. Just like that guyz velocity porting, maybe the ducar is overkill and the loncin is the correct size in which case i can get some good performance out of the loncin.

ideas/opions please

 

[Mack]

I suspect your only option will be to modify one or two of the stud holes in the ducar head and bolt it to the loncin motor. Bore the loncin and install HC 54mm piston with 13mm pin. Then you'll have a ripper.

 

[noidea]

yea. Ill just get the head studs opened up 1mm each hole... should be plenty. Then take 1 or 2mm off the rocker shafts. Cant wait to get the engine running! First layer of the JB weld has set now. Been on the heater all night. I should only need to do one more layer. Clean up the zorst port, blast em all get it milled and get riding again!

 

[Mack]

You will have to check the cam timing. How many teeth on the different cam sprockets.

 

[noidea]

will check now.

JB weld worked sweet, have closed the port down to the size of the manifold, finished cleaning up the combustion chamber and finished the exhaust port now. Only need a little more jb weld to get a flat surface at the manifold surface. Should still have the engine running next week sometime. Thinking about a hc piston atm tho.

 

[Mack]

you may have some more problems to overcome yet

 

[noidea]

Ok.

Cam gear problem: The gear off the ducar is much larger than the gear off the loncin. But the bolt pattern is exactly the same so i should be able to bolt the loncin cam gear to the ducar cam and that be solved.

Any other problems you can see happening let me know.

Next layer of JB setting at the moment then the head is ready to get a valve grind, get the stud holes opened up a bit and then bolted on!

 

[Mack]

When you drill out the stud holes you will have to keep in mind the cam gear alignment. Also because of the huge dome in the big valve heads you are going to cop a big drop in compression, so you may have to look at decking the head and cylinder.
That solves a big problem the cam sprockets matching. You will still have to degree it in to be sure it is right. Hopefully after these mods the cam chain will be the right length.

 

[noidea]

Yea.

Compression is my main concern at this stage, the ofset of the cam is going to be 1/2mm... 1mm max, so not really enough to derail the chain but possibly enough to cause some wear on the gear/chain but im not too worried. Im going to try and get a high compression piston to suit, have emailed carter but am struggling to find some online thumpstar stores. who do you usually deal with? Im not too fussed about importing, it will probably end up cheaper that way.

 

[RD RACING]

looking into this post, noidea i feel you would have been much better off in regards to these separated mods if you stuck with the original and worked original comp parts from there. this would save many headakes ect ect . the chinese make many non compatable parts from engine to engine, you should use the good lifan engine and buy the good needed upgrades as we have done with one of our lifan engines, very very torquey plus . its all to do with undo and bolt on these days, saves all the headakes.

 

[Mack]

He doesn't have a Lifan thats the trouble. When you started porting the Ducar head I didn't realise the Ducar motor wasn't going, and the head would be used for the Loncin.

The fact that the cam gear is a straight swap over is a bonus. If you are prepared to get a hc piston then you can aim to deck or raise the head to bring the cam timing into correct position, therfore negating the need for any extra work here. It may even be spot on as is. I would try and make sure the cam gear lines up properly though. Front to back does'nt matter, just sideways.

I think some of your studs should line up correctly. Do they? If you found that some studs lined up or the allignment of some stud was correct for the camgear position, then keep that hole or holes and use knock pins here. Does that make sense? Then redrill the others. Don't worry about the combustion chamber being square over the top of the bore. You can relieve the dome in this area if you have too and also the valve pockets. Deciding to go with the hc piston saves you a fair bit of mucking about.

You should be able to get a 52.4 or 54mm piston with the 13mm pin from many places in Aus. I know there are members here who are supposed to sell them. They should PM you if they can help.

 

[noidea]

working on the engine is the whole fun of it RD!!!! Whats the fun in buying an engine and just 'bolting' parts on... no challenge there.

At the moment my only concern is the compression. I think i will drop from about 9:1 to 8:1 which should be enough for the engine to run. The gains in valve/valve seat gains should be enormous in terms of engine higher rpm power. At the moment, i will be drilling out the head stud bores. The rocker shafts may then be affected in which case i will then turn down 1mm of the rocker shaft and the head should be on! Then, once i find a reasonable HC piston ill order that and put it in.

Mack, i have pm'ed a few guyz off the forum regarding a HC piston for a 52.?? piston.

I did get pretty annoyed that the engines wernt compatible, but hey... when its running 10x harder than it was before the real satisfaction will hit!!

ps, wish it had a lifan...

Ill keep you guyz posted, and cheers for the feedback

anyone with a 52mm HC piston that takes 13mm gudgeon pin please U2U me or email at [email protected]

 

[noidea]

Been looking round and found a few on the tbolt site... Am i going to get one for much cheaper than $100ish?

update: Cleaned up the intake manifold today and matched it too the head. All ive got left to do is sandblast the lot and get a valve grind and the machining done...

 

[noidea]

Head is all ready to go. Stud pattern semi sorted, doesnt need machining.. just need to work out something for the dowels. Am going to see a mate running a mechanic business see if he can grind my valves for a lil cheaper.

Carter has given me a price fo $--ish for a HC piston, gotta make sure its the one im after first.

Im going to skip the sandblasting idea for now coz im worried about the jb weld thinning out quicker than the alloy, i have smoothed the intake over with sand paper, and given the exhaust a very light polish. Combustion chamber is polished up ready to go. Bike should be running this week!

 

[noidea]

Alright, getting mighty close!

Mack, i can get one dowel or knock pin in, and the head sits pretty tight on the bore, both not moving much at all.

The combustion chamber sits a bit off, Im not sure if i should worry about this or not?

Picking up the head tomoro with a fresh valve job. Ill get them to chuck the valves in at the same time for me and then i will go home and depending on the replys i get here either try and work out a way to machine the head or just let it sit a bit off centre.

Heres a pic of the head sitting on the barrel, let me know what you guyz recon!

http://www.mypicpal.com/jarvie/My Photos/photos/problem.JPG