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350LC transfer port heights


DougW
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Just popped the barrels on the 350lc and done a quick measure on the main transfer heights .

lh barrel 42.4 one side 43.0 on the other.

rh barrel 42.6 one side 43.6 other.

differences seem a lot to me, but will they make a significant difference on a road bike engine ?

 

Opinions please !

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Assuming the barrels are "standard" I doubt it would make "that" much difference, but if they've been ported already I'd be getting them matched by someone who knows what they are doing.

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46 minutes ago, Tom Mac said:

Assuming the barrels are "standard" I doubt it would make "that" much difference, but if they've been ported already I'd be getting them matched by someone who knows what they are doing.

That is one of the options I am thinking !

Exhaust ports are up at 28mm , barrels have been relined because of lumps out of transfer ports.

I guess the new liners have been matched to the bodged original porting job.

If this was going to be a "Fast" engine I would definitely be getting the barrels to a proper grown up tuner, but as this is for road use, top end not particularly important (but obviously nice), I am more concerned with not loosing bottom end and having a bigger than usual midrange flat spot.

So after a "nicely" running road engine, that is fairly reliable. I have no desire to go back to the days of feeding highly tuned LC`s on a constant diet of pistons and cranks !

I had a Terry becket "Road Tuned" LC in the 80`s that I put about 10,000 miles on before blowing it up abusing it on the track, so think that is possible.

To add confusion, It will be running on the YPVS microns it came with , as I have no standard 4L0 pipes, or have the option of a set of 31K YPVS standard pipes

Torn between getting it back together and see how it goes, (so close !) or spending more and waiting till it is "Right".

 

 

Edited by DougW
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I agree with Rich, lifted exhaust ports and Microns will be lightswitch powerband material. I'd say it would be worth matching the transfers though, as that usually improves drive and smoothness, which is what you're after. If it's any help I can do that for you?

 

 

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  • 2 weeks later...
On 12/25/2020 at 9:56 AM, Martin77 said:

I agree with Rich, lifted exhaust ports and Microns will be lightswitch powerband material. I'd say it would be worth matching the transfers though, as that usually improves drive and smoothness, which is what you're after. If it's any help I can do that for you?

 

 

Thanks Martin.

As the people who re lined the barrels seem to think those measurements are “ normal” I’m going use the standard ypvs pipes to run it in and see how it goes. Once I have a few hundred miles on it I’ll get it dyno’d and make a decision on whether to whip the barrels off and let someone such as yourself tidy it up.

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Sounds like a plan..

To be fair to the people who relined the cylinders, if I were given a tuned (good or otherwise) cylinder and asked to reline it, I would be inclined to copy what was there, otherwise the customer might be a bit miffed to have it returned to standard in the process. (Just being devil's advocate here... I've seen some terrible relining jobs!)

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Meanwhile , this has arrived.

What could possibly go wrong ?

 

20210104_131214x.thumb.jpg.8fb9bb6812871ce40670f5ff41a97589.jpg

 

(I don`t think I will risk touching the LC Barrels myself, but I have the Stan Stephens write up of the DT175 and a couple of victim barrels to play with)

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  • 2 weeks later...

Update.

Looked at fitting the PV exhausts, brackets need repositioning, but boy are they heavy.

So microns on.

Repacked, not too loud at low revs... 3 heat cycles in sounds good even with throttle slides not balanced and air screws just set at 1.5.

It has the original 4L0 carbs that have been modified in a professional looking way to the original or the dealer Yamaha mod, will have to see how it feels.

Got a set of disks to clean up, fit to the nice eBay front wheel I picked up, wait for a better covid situation, MOT , few hundred miles then Dyno time.

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I just remembered something , the Yamaha parallel twins respond well to at the junction of the A transfer inner wall and bore step that down about 5mm

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On 1/20/2021 at 2:42 AM, 2T Institue said:

I just remembered something , the Yamaha parallel twins respond well to at the junction of the A transfer inner wall and bore step that down about 5mm

I think they had been lowered on my barrels pre re-linering, back to standard looking now with the re-lined barrels.

3 stationary heat cycles in now, sounded worryingly crisp with a few blips up to 8,000 ish yesterday. (-1 C here then) 

Its got the original 4L0 180 mains in that it came with at the moment, thinking of putting a couple of 220`s in for peace of mind and see how it feels.

Got to wait now until covid situation a bit less serious and get an MOT for it to do some running in with a bit of load.

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  • 4 weeks later...

i wouldnt be doing any riding with microns and standard mains.... easier to rejet than re piston.

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It has 190 mains in that it came with , it had been running that jetting for a while judging by the bore wear and Amount of carbon. A few minor scuffs on pistons no major signs os seizing.

It has the first 4L0 carbs that have some professional looking mods to the pilot circuit that don’t match anything I have seen on web, like the dealer mods. Can’t remember precise details but it’s got the bigger pilots.

giving it a few blips up to 8,000 when air temp around 1 C it did sound worryingly crisp to me ( been playing with RM and KTM 2t jetting for last 15 years so have a fair idea about 2t sounds on different jetting now)

With that in mind I have a pair of genuine Mikuni 210 jets to go in before it sees any high revs.

Counting down the days to March 1st when it’s insured and can take it for MOT. 

I have an 18 year old son to set an example too, so no illicit late night test runs, like the neighbour used to do with his racing F2 sidecar, or someone a little closer to home on unregistered race bikes....

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  • 2 weeks later...
Posted (edited)

Well, according to internet lore, the main jets ( actually 180 ) are too big, even with microns, for the early 4L00 carb, with standard air box and filter.

Mine appear to have the Yamaha suggested mods and another drilling through a blanked bit of casting to connect the pilot air circuit to the carb vent, which was as mikuni intended in some versions, and probably like the later carb ?

Its definitely very rich used nearly a full tank in 30 running in miles, and improved with 27.5 pilots changed to 22.5, and one needle clip moved up one and one down one notch so both on position 3 !

Some m5 brass grub screws ordered so I can remove the brass ball blanking plugs, and the nice neat alloy plugs on the modified drilling’s, clean them out, tap them and re plug them.

170 mains ordered and I’ll go back to the 27.5 pilots.

This takes it back to Yamaha recommendations.

Edited by DougW
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Must dig out the 31K ypvs carbs I have stashed away for the 350LC\YPVS hybrid long term project , give them a good clean and try them on it.

They where full of crud when I got the bike 20 years ago, cleaned them, evicted the rodents from the engine, stated it and ran it fo a few seconds to check it worked, then pulled it to pieces and stuck it in the loft.

Its still up there, frame re coated , yolks fitted and not touched since.

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Well that didn’t go as hoped. 

31k ypvs carbs seemed fairly clean, gave them a good ultrasonic clean anyway.

Rebuild kit pilot, mains and float needle fitted.

idle screws carefully synchronised.

It runs awful with these carbs.

Not even going to bother riding it with them.

Internet suggested you can bolt on the YPVS carbs and the jetting is acceptable. 

Didn’t take the brass balls out to clean behind though, still waiting delivery of brass grub screws.

Got a local guy lined up to look at the ports, Richard Slinn, Trick Tuning, but really want to get a few hundred miles on the barrels before pulling it apart again.

I have had trouble getting the throttles balanced, seems good, ride, check, out again. Repeat.

New oem throttle cable arrived now.

 

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Original carbs blanking plugs removed and air bleed jets behind blanking plugs cleaned out. Grub screws fitted instead of blanking plugs.

Getting better. Flat spot not as flat or wide.

Down 10 on mains next.

Rides nice on new bt46, pleased considering only rebuilt forks to standard spec and not fitted correct springs or compression damping valve, and back shock not touched.

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170 main jet , needles on clip 2, better.

Needles on clip 1 , better again.

Standard gearing, but 90 profile rear tyre has raised the gearing a touch.

Thinking that combined with the lifted exhaust it could do with gearing down a touch

It still seems rich, needles don’t seem badly worn, but I’m wondering about the needle jet / emulsion tube.

wacking throttle open from tickover no trace of lean bog.

Float heights triple checked at 21mm from gasket face.

Should probably put a piece of clear tube on overflows and check actual fuel height.

( Martin77, only reason barrels not going to you is I have a bloke practically  on my doorstep that I can drop off and pick up the bits. Totally paranoid about things going missing in post, been bitten before )

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12 hours ago, DougW said:

 

It still seems rich, needles don’t seem badly worn, but I’m wondering about the needle jet / emulsion tube.

 

Any concern on wear on either of those and I'd be replacing them with new.

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Posted (edited)
32 minutes ago, Tom Mac said:

Any concern on wear on either of those and I'd be replacing them with new.

Agreed.

I`m wondering whether to go for the original early spec needle and needle jet its running in its original, or go for the  later spec parts.

Looking at the jets in Haynes, the air jet in the later carb is 0.8 not 0.5, so I think I`ve just answered my own question, unless I drill the air jet out to 0.8 stick with original needle/needle jet spec.

Always wondered how 160 jets worked in early carbs and 220 in later. Air jet bigger in later.

Off to Allens then.

Edit to add.

4H16 needles and 345 0-6 emulsion tubes on their way. Its a good job small bits of brass don`t LOOK expensive.

Edited by DougW
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Just catching up with this... nice to see it improving little by little. Takes time eh! 

On 3/16/2021 at 10:31 PM, DougW said:

( Martin77, only reason barrels not going to you is I have a bloke practically  on my doorstep that I can drop off and pick up the bits. Totally paranoid about things going missing in post, been bitten before )

No problem! I've not heard of him much, but I've seen some of his work in pictures and it looks neat.

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New needles and needle jets, feels nearly civilised now.

Need to check the timing, quick run on local dyno, then barrels off. 

For my own benefit, I'll put a degree disk on and note all the current port timings,  make a port map, then give barrels to a grown up.

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  • 4 weeks later...

31K standard pipes on, better again, not a flat spot as such any more, but with one tooth off the front and one tooth on the back was expecting a much livelier engine.

Checked the timing today with newly arrived  dial gauge and adapter.

  I had left it in the same position as when I got it after the rebuild, as my original dial gauge adapter had gone walkies , last seen around 1988...

Any way, it was set to 0.7 mm BTDC.

Set it to factory 2.0mm (standard compression and massive squish at the moment, will back it off a bit if that changes).

Better again. Its useable as road bike now, which is what I want this one for.

I think its now as good as its going to get until ports matched up, best book a slot for getting them looked at.

 

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Barrels dropped off at Trick Tuning this morning,  he's already spotted transfer liner angles wrong as well as the different heights.

Pleased in a way as it should be improved when sorted, but less pleased thats its definitely not the stock porting that was stated by the re liner. Admittedly the barrels had been badly "ported" before, but to have them returned as they where with no comment,  and when questioned to reply that mismatched port heights is "usual" , not impressive. 

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  • 3 weeks later...

Barrels back. Trick Tuning had one of the Mitaka pistons, he shamfered the skirt base, it was like a knife edge, you could see it had picked up slightly at the rear of the piston.

Tomorrow I’ll do the other piston, and if the new 0.15 mm base gaskets arrive rebuild it.

YPVS reed blocks and a 5mm spacer going in, barrels came modified for the ypvs reed block but had standard 4L0 reed in when I got it.

Run it in for a final 200 miles, should have made or acquired or thinner copper head gasket by then to get squish around 1mm.

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  • 2 weeks later...

Result. Pulls cleanly through mid range. Feels nice and torquey . Piston clearance seemed tight at 0.04mm if my use of a bore gauge and micrometer is correct, so best get a couple of hundred more running in miles done, not so much of a chore with how its running now.

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  • 4 weeks later...

Five hundred odd miles done, ran it to 8000 through the gears two up down the local bypass, runs well.

Easily dispatched colleagues 2 litre diesel BMW and Audi on the run back from the pub yesterday lunchtime.

Very happy with it.

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