1989 kr1 with kr1s bits and bobs

maccas · Post by **maccas** » Sat Apr 21, 2012 9:36 pm

Since the dyno I've been fiddling around deciding what to do with the barrels on my bike, basically to wake the bike up a bit I'm going to need some bigger ports. I have a set of kr1s barrels that have had some work done and they have had some welding at the back. Whether this is because they had cracked or whether it is to prevent cracking is hard to tell. The base of the barrel has been skimmed by about 0.3mm:

The welding looks to have been done by BDK but I'm not sure about the porting. The secondary transfers have been widened but towards the exhaust port in order to run stock pistons.

Here is the port map, the transfers aren't very symmetrical

So with the barrel being shortened, running a stock base gasket will upset the port timing and the squish, but as I'm going to run vertex DTR pistons then the problem is made worse due to the higher compression height. Anyway I need to decide whether to go with these or get my kr1 barrels modified.

I've got another single barrel that has huge ports and some other mods I'll do a map of that now.

Dan

maccas · Post by **maccas** » Sat Apr 21, 2012 10:29 pm

I think the ports on this barrel are overkill for my set up, I can't see it having much midrange but could be wrong.

I'd be interested what people think about that port spec. I'd have thought somewhere between this and the other one would be good.

Dan

maccas · Post by **maccas** » Sun May 06, 2012 8:24 pm

Well its been a while since I've updated this thread!

Went to the practical sportsbikes trackday at cadwell at the end of April:

(Picture stolen from the diffrent strokers site, hope you don't mind Tim)

Had a really good day but the bike nipped up on me at the end of park straight. Grabbed the clutch quick and it turns out damage was minimal, you can just see where the rings dug in on both bores, very lightly picked up.

Since then I'm re-jigging the top end and uprating the cooling system, whipped the engine out last saturday and brought it back to uni with me so I could work on it in my living room

(not the worst thing I've done, once spray painted a full set of fairings in my bedroom lol, the overspray was a bit of a problem haha)

Heres the yfz450 rad i bought off ebay uk:

82 quid posted so pretty pleased really.

Mj sent me some stuffers for the reed blocks which i've modified today to fit the 35mm inlet manifolds, thanks again MJ!

I've sent my cylinders off to get the KIPS ports widened and raised and also the PV's blending into the KIPS tunnels a bit better than I was able to do with the dremel.

In the mean time I've been looking at the head that was on the bike:

It has been worked in the past and has been skimmed so that the edge of the squishband is flush with the face of the head, it is not recessed in any way.

The fitted clearance volume is 9cc which gives 8.25:1 CCR (26.5mm from top of exhaust port to TDC) and 14.85:1 uncorrected which for me running on 95 RON I think its a bit high really and may be helping to cause my early rpm peak.

I'm going to increase the head volume to give 10cc fitted clearance volume which equates to 7.53:1 CCR (a touch more than stock) and 13.46 uncorrected which will be fine for running 95 ron fuel.

Squish as the bike was set up was a bit crap to be honest, the squish angle was not suitable for the piston as the squish clearance increased the closer you got to the centre of the bore which will reduce squish velocity which won't have been helping matters either I don't think.

I'll aim for a .8mm squish with a suitable angle to match the new vertex pistons I am going to fit.

Dan

mj43 · Post by **mj43** » Sun May 06, 2012 10:16 pm

Dan

Dig up the spreadsheet I did for head calcs.
I use a 30mm radius dome and 6mm wide squish, ,I think dimensions are in the sheet.
That is for TZ pistons - modify squish angle and other bits as appropriate for the Vertex pistons.

Have a look on the old Teamsparrow website for port maps, it hasn't been maintained in many years so may be down?

maccas · Post by **maccas** » Sun May 06, 2012 11:04 pm

Hi MJ,

I've been playing with that spreadsheet today as it happens!

Is there like a maximum safe limit on squish velocity that shouldn't be exceeded for a given engine speed or something like that?

Or is there a particular figure that it would be good to aim for?

Basically as the bike was set up with stock pistons the squish was 0.75mm at the cylinder wall (a bit tight I know) and 0.98mm at the edge of the squish band near the centre of the cylinder. Not ideal at all.

Cheers,

Dan

TwoStroke Institute · Post by **TwoStroke Institute** » Mon May 07, 2012 6:11 am

No maximum MSV figure just has to suit the application. 0.75mm squish is fine.
The first is the only one to use hopefully the ex duct hasn't been hogged out. You would just take the main ex port up to 26mm and the B transfer to 38,5.
Second has multitude of sins worst is the main ex has been taken out to nearly 80% width of the bore.

banditharry · Post by **banditharry** » Mon May 07, 2012 10:55 am

im running .75 squish using a stardard head with yamaha 26j pistons and modded barrels, tried .7 and it blew the head gasket for some reason so i upped it with no problems since.

Where abouts did you get that rad from? looks like a nice bit of kit.

maccas · Post by **maccas** » Mon May 07, 2012 11:27 am

I got the rad from this seller:

http://www.ebay.co.uk/itm/RADIATOR-YAMA ... 20c53c9654

Postage was quick too, no hassles at all.

Haven't tried it to see if it will fit within the fairing though yet, JanBros has and he said it will need some padding between the fairing and rad to prevent damage.

Lozza,

I take it you are talking about the portmaps higher up the page, I've done a port map of the barrels that came off the bike, I will take a pic now

Dan

maccas · Post by **maccas** » Mon May 07, 2012 11:59 am

Kips ports are small and lower than the main port, through digging through this site and researching peoples specs and the results they have got from them it is clear that the main port is too high to give good midrange grunt. With the vertex pistons having a higher compression height I have the option to effectively lower the cylinder by 0.5mm or so. Coupled with thinner base gaskets I can go even lower if needed. (with adjustment to the head of course)

I am doing something a little bit different and getting the KIPS raised so that the top edge is level with the main port at 26.5mm from the top of the cylinder. What it will do I don't know but I'm going to try it. Getting the KIPS widened too.

Rest of the cylinder staying as it is.

I might lose midrange drive with the exhaust port the size that it is but then I have the option of my other set of cylinders that are actually closer to stock than the port map at the top of the page makes out (forgot about the chamfers around the ports) so i can get them cut to a more suitable spec.

I will update once I have the cylinders back

Dan

mj43 · Post by **mj43** » Tue May 08, 2012 8:19 am

Dan

The welded barrels might be ok for bimbling around on the road but if you want to make some serious power (for a KR) 60hp+ they won't last more than a few dyno runs.

My best set of barrels even with a strengthening bridge across the back failed after two race meetings. Barrel cracked across the front - strengthening prevented the rear cracking.

I now plan to go to a crank with 3mm over length rods and lift the barrels 1mm (TZ pistons 2mm shorter) by bonding (welding?) a base plate to the barrel to put a bit more meat on it. Also I am going to use some shaped 2mm steel washers below the barrel nuts to spread the load. Aim is to reduce the flex in the mounts to stop the cracking which has plagued my engines for the last 4 or 5 years. Once that is sorted then I can push the torque curve further.

Still don't agree with Lozza about the height of KIPs ports

maccas · Post by **maccas** » Tue May 08, 2012 8:58 am

Hi mj,

Yep preferably i would like the kips higher than the main port but because the main port is high already i didn't want to go straight to that spec. This way if i need to i can get the kips lifted at a later date after i see what the current spec does on the dyno. I expect top end power (10k plus) will be pretty good but below that i'll be lacking drive due to the high main exhaust port. If the high main port is killing things then i can lower the cylinder with thinner base gaskets and then get the kips raised further. i have a spare head that i can get machined to suit. The transfers are already high at 38.5mm from TDC as well.

Ok i take your warning regarding the welded barrels. They are about 0.4mm shorter than standard. I'm guessing they have cracked before and thats why they have been welded

I thought that is what you might have ended up doing with the crank. I'd be interested in seeing the results.

Dan

TwoStroke Institute · Post by **TwoStroke Institute** » Wed May 09, 2012 3:19 am

Whatever you do don't make the sub and main open at the same time, that is proven to loose mid range. The main port is not to high at 26.5mm going up to 26mm would be even better. Your problem is you have NO blowdown time or area. Fix that and you will be much better off. Subs need to extend to where the piston cut outs are.

mj43 · Post by **mj43** » Wed May 09, 2012 6:20 am

Dan

It would be interesting to see what effect raising the main exhaust port will have as TSI recommends.

However, the motor has more port area than a stock motor but makes less power. With the crankcase mods etc I would expect to see your motor making at least mid to high 50's on James' dyno.

So before modifying the barrels I would revisit the dyno and make sure that with the stuffers in you are making the expected power. If not then there is something wrong. I would be happy to pop down - can bring a few bits along that you can try to eliminate any problems you might be having.

TwoStroke Institute · Wed May 09, 2012 11:54 am

I just saw you have a 9cc head volume, is that on the engine or flat plate volume(fpv) ?
A extra 0.5mm gasket under the cylinder will help, but your ignition is your best friend here. You have peak power at sub 10,000 so your pipe temps are not in sync with the rpm. Hence you hit a brickwall.
How much advance do you have at and after 10,000?

maccas · Post by **maccas** » Wed May 09, 2012 2:52 pm

MJ,

You are right, that would be the best thing to do. However the job is almost done on the cylinders and I should have them back early next week. In hindsight that is what I should have done. James is a good 130 miles away though and I have to hire a van etc when going down to see him so when I next go I will be taking the 3xv with me too to make it worthwhile with the van hire etc. Unless I can go with one of my mates bike trailers. Either way I will definitely let you know when I am next going down. Will be good to meet you

The reason I got the kips cut is because I wanted them to be closer to standard KR1S spec than the KR1 spec that they were at. If it turns out that I need to start a fresh with another set of KR1S cylinders then that is what I will do. There is always that option.

Lozza,

For now i'm going with the KIPS the same height as the main port, if it shows up thats its crap on the dyno I will get the cyls re-cut or look for another un-molested set to start a fresh with.

9cc is fitted volume. Peak advance set at 10000 dropping to half that value at 12k. Guessing too high for that compression ratio. But when on the dyno on the day I didn't know that I only had 9cc heads. Now it makes more sense.

I'm going to go for 10cc fitted volume and stick to that figure, the head wants re-cutting anyway as the squish angle is miles out.

Regarding blowdown yep I see what you mean with exhaust 26.5mm from TDC and transfers at 38.5mm from TDC that gives me 29 degrees of blowdown.

What do you mean by blowdown area? The area of the exhaust port that is open at the instant that the transfers open? Is that right?

With 26mm from TDC to the exhaust port opening that gives 30.3 degrees of blowdown so not a vast improvement. If the transfers were lower then I could get more blowdown time?

Dan